Jekyll & Hyde

You may be looking for The Strange Case of Dr. Jekyll and Mr. Hyde or its stage musical adaptation Jekyll & Hyde.

He can be your angel... or your devil.

"I guess we're all two people. One daylight, and the one we keep in shadow."

— Bruce Wayne/Batman, Batman Forever

When a character and his Evil Twin, Evil Counterpart, or Shadow Archetype are really the same guy after all. Or, sometimes, a completely different character is sharing body space with another. The point is, the villain lives inside the hero's body, and therefore hides in plain sight. The hero is trying to catch himself.

If the two personalities are aware of each other, this becomes a case of Gollum Made Me Do It. For a more mundane version, see Mood-Swinger. See In Vino Veritas if the change is alcohol-induced (you could call it "Dr Jekyll and Mr Jack Daniels"). As an evil “Hyde” personality's crimes are outside the good “Jekyll’s” control and the “Jekyll” is usually unable to stop the “Hyde” emerging, this is often a case of being Driven to Villainy.

Sometimes, though, the “Hyde” is not really evil; it may just be more instinctual or capable of using violence when necessary... See Wikipedia Behavior for the wiki version of this, also known as "Dr. Pedia and Mr. Trope". Also, a "Jekyll" persona isn't necessarily entirely "good" either — it may just be subtler or more self-controlled. After all, in the original story, Jekyll created Hyde as an outlet for his darker impulses, thus acknowledging that he had such impulses. Occasionally, the situation can be resolved (not necessarily favorably) with a Split-Personality Takeover, or with a Split-Personality Merge that reconciles both sides into a healthy whole. See also Superpowered Evil Side and Helpless Good Side.

The trope name comes, of course, from The Strange Case of Dr. Jekyll and Mr. Hyde, by Robert Louis Stevenson. The dual nature of Jekyll was actually originally a Twist Ending in the case of that story, but the book became famous and now it no longer surprises anyone. Most adaptations of the work focus on the dichotomy from the start. Other occurrences of the trope may still manage to surprise if they’re well done.

The real-life example of Deacon Brodie (cabinet-making pillar of the church by day, burglar by night) is said to have inspired Stevenson, as did the story of Horace Wells, a pioneer of medical anesthetics. While researching chloroform by testing various dosages on himself, Wells unknowingly built up a dangerous level of the drug in his system, and ultimately attacked two prostitutes with sulfuric acid in a state of intoxicated paranoia. He then committed suicide after sobering up and learning what he had done.

Specific variations include:

• Hyde Plays Jekyll: When the Hyde personality is in control and pretends to be Jekyll in order to fool others;
• The Jekyll Is a Jerk: Where the Jekyll personality as well as the Hyde turns out to be morally shady if not outright evil.

Since the fact that the hero and the villain are the same person could often be used as a twist ending, beware of spoilers on this page.

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Examples:

Anime & Manga

• The 100 Girlfriends Who Really, Really, Really, Really, Really Love You: Kurumi is usually a sweet girl, but once she becomes hungry (which is almost always), she becomes aggressive until her hunger is satisfied; a human Morpeko, basically.
• JoJo's Bizarre Adventure: Golden Wind: The underboss of Italy's ruthless crime organization Passione is an eccentric, rather dorky young man named Vinegar Doppio, who is the most loyal subordinate of the mafia's secretive boss, and communicates with him via "telephone", AKA talking into random objects he hallucinates as telephones. As it turns out, he doesn't realize that he and the boss are one and the same, the latter hiding in Doppio's subconscious and only surfacing when in danger of others coming close to figuring out his true identity.
• Kyo and Kyoshiro in Samurai Deeper Kyo. Subverted in the manga, played straight in the anime.
• Tsubasa from Beyblade: Metal Masters has a dark side when he beyblade battles, making him obsessed with winning, going a bit mad. (He usually loses as a result)
• Bakugan: Masquarade is revealed to actually be Alice, the Friend to All Living Things and Nice Girl of the main team. The Jekyll and Hyde complex was created due to being around her grandfather's laboratory at the time of an experiment that released powerful negative energy into the area. Masquarade is a cruel, sadistic, and incredibly powerful and strategic Brawler that plagues the main cast constantly, Alice is a Non-Action Girl Pacifist that wishes avoid fighting altogether. This is also a case of Gender Bender. By the end, the truth is revealed to her, and she is driven to abandon her team for fear of turning into Masquarade at inopportune times. Ultimately, a Split-Personality Merge occurs. Masqurade instead manifests himself occasionally as a Spirit Advisor in Brawling to Alice, who finally becomes an Action Girl (while still keeping her Nice Girl personality).
• Magical Project S: Misao Amano's normal self is that of a stereotypical Shrinking Violet friendless, blue-haired ill girl. However, this persona falls away when she's transformed into Pixy Misa, the manifestation of her deeply repressed id: an egomaniacal jealous Dark Magical Girl trickster.
• Inverted with Lucy/Nyu from Elfen Lied. Lucy, the evil counterpart, is actually the original character (sort of), while a blow to the head caused her to go into passive, non-lethal "Nyu" mode.
• After the protagonist of Death Note pulls a Memory Gambit, he devotes himself to catching Kira, not being able to remember that he himself is Kira. The instant he regains his memories, he reverts to his original personality and begins killing once more.
• Gankutsuou has The Count of Monte Cristo possessed by the titular demon which completely submerges his original good personality as Edmond Dantes. This is only a part of the story, though, as it was Edmond's own lust for revenge that summoned Gankutsuou to him, to begin with, and Gankutsuou has no personal interest in doing any harm to Edmond's enemies or their loved ones, only fulfilling his own end of the bargain. When it seems that Gankutsuou has fully consumed Edmond, he simply walks away from the person he was about to kill as revenge by proxy, without so much as looking back.
• Mnemosyne subverts this in its penultimate episode. Rin, who was sucked into a jet engine, and presumably got her memories mixed up from having her brain turned into a shake, is seen working at a MegaCorp by day and killing other immortals and collecting their time spores by night. Mimi even lampshades it. However, it turns out that the latter was actually Laura in a cyborg body designed to look like Rin.
• In D.Gray-Man, this is the case with Tyki Mikk and possibly the rest of the Noah... Though probably just Tyki (who 'loves humans'); his mind remains constant between sides, and he gave his little friend the silver off a murdered exorcist's coat as a present. If Allen had gotten it, the plot might have run a bit differently... Also, White Tyki appears to be effectively dead. His identity took a serious scramble back when Allen thought he'd cut the evil out of him and got a really superpowered especially evil side instead. Surprising he pulled himself back together, but he's different. The Noah are activated out of normal humans, whenever a seat is left unfilled by a death in the family, and for the most part memory is not continuous from incarnation to incarnation, but those persons are still subsumed into the Noah identity once activated. This is one of the things Allen is trying to prevent happening to him. Whether Adam the Millennium Earl and the Fourteenth have died and recorporated before is not clear; very possibly they haven't. Road is over thirty five now; it's possible Adam has kept that rakish young face for thousands of years. (And covered it with a grinning balloon thing in a goofy hat about as long. Mysteriously.)
• Hellsing has Yumiko Takagi, sweet and gentle nun, kept on hand by the Vatican's secret team of assassins for her alternate personality Yumie, who is a berserker killing machine (and darn good with a katana).
• Harumi Chono from Paranoia Agent. Tutor for Ichi by day, a prostitute named Maria by night. The way they communicate with one another? Leaving messages on their answering machine for each other.
• Allelujah and Hallelujah in Mobile Suit Gundam 00. The former is a soft-spoken Nice Guy who is willing to save innocent lives while the latter is an Ax-Crazy sadist who takes joy of torturing his enemies. Both personalities are aware of each other's existence, causing Allelujah to be afraid that allowing Hallelujah to control him would make things worse unless it's necessary such as defeating powerful enemies.
• Psychic Squad has Mirage, who is also Phantom Daughter. Both personalities are hiding in and from Yuuri, AKA The Doll, an ordinary schoolgirl "built" for infiltration that they are spending an increasing amount of time in, to their boss' displeasure. Additionally, there's a fourth personality that the other three are unaware of.
• In Kämpfer, Akane is a sweet, shy, bespectacled girl who often hangs out in the library. When she turns into a Kämpfer, then she becomes a real mean, foul-mouthed, trigger-happy bitch with a pair of pistols.
• In Project ARMS, Keith Black has his original, rather sweet personality and is gradually taken over by his "father" Keith White, who is a demented maniac with a God complex. Alice herself is split into "White Alice" and "Dark Alice".
• In the manga O-Parts Hunter, the main character Jio has Satan inside of him. Satan comes out when Jio's or his friend's lives are threatened. That is, until the time skip. By the end, it's revealed that Jio is Satan reborn. Jio is Satan's dual personality.
• Rosario + Vampire has Moka Akashiya, a shy, well mannered girl who is not always confident. Her true self is a thuggish brute of a vampire who can kick the snot out of anyone. And by true self, we mean the personality she was born with. Her "Jekyll" half was artificially created.
• Amuri in Star Ocean has Perrier/Vernier La Mer. Perrier is the real personality who, as a result of torturously cruel parenting, subconsciously created Vernier as a defense mechanism and referred to her as her older sister. When seeing her reflection, Perrier would see Vernier looking back and talking to her, always taunting and insulting her. Vernier does not take full control of Perrier, though, until she is pushed into a state of extreme terror.
• Jūgo of the Scales in Naruto is a Gentle Giant who lives in constant fear of what he will do when his bloodline transforms him into his Curse Seal self.
• One Piece gives us Cavendish; When awake, he's a gentlemanly Bishounen of an Attention Whore. But when he falls asleep, his Superpowered Evil Side Hakuba takes control, and goes on a violent spree so fast that no one can see him. Unfortunately, he also has a bad tendency to fall asleep in the middle of the day.
• Yu-Gi-Oh! has Marik and Yami Marik, the latter being the personification of Marik's rage and anger. He eventually hijacked Marik's body and tried to kill his other self to maintain complete control.
• In Yu-Gi-Oh!: Capsule Monsters, the Millennium Ring split Alexander's soul into two halves, one his peaceful side and the other his war-mongering side. The evil side notes that without him Alexander could have never conquered half the globe.
• The Muten Roshi's maid Lunch from Dragon Ball, in her usual form she's a friendly blue haired woman but whenever she sneezes she turns into a mean and violent blonde woman, she reverts back with a second sneeze and has no memory of her actions in her mean form.
• The Lupin III: Part II episode "The Two Faces of Lupin" involves a man who goes around impersonating the real Lupin, stealing whatever he sets his eye on before the real one can, but also murdering in cold blood. The impersonator teams up with a former friend of Lupin turned traitorous, Dr. Normil, who manages to convince the real Lupin and his gang that the horrific acts of violence the impersonator is committing are actually the result of Lupin having "Hyde's Disease", which causes him to turn violent at the stroke of midnight.

Comic Books

DC

• Batman:
  • Harvey Dent, a.k.a 'Two-Face' has this going on, with the split represented by Harvey's own split face; his unblemished, handsome right side representing the good, noble District Attorney Harvey Dent, and the scarred, mangled left side representing the malevolent, vicious criminal Two-Face. In his case, the choice between 'Jekyll' and 'Hyde' depends on the results of a coin toss, with good or bad triumphing depending on which side the coin comes down on. This is singly most obvious in his debut appearance, where distinct similarities are drawn between him and the story. In fact, his appearance was inspired by a poster for the Spencer Tracy film.
  • Batman: The Dark Knight Returns turns this on its head. Recent breakthroughs in plastic surgery have restored his face to normal, but at the unforeseen cost of forever destroying the "Harvey" half of his personality, and permanently leaving the "Two-Face" half in complete control.
  • The Ventriloquist and his puppet, Scarface. Thought most people (including some writers and readers) act as if Scarface were actually alive.
  • The Elseworlds comic Batman: Two Faces has Bruce Wayne in the Jekyll role, trying to create a serum to cure the split personality of Harvey Dent. We basically end up with "Dr. Batman and Mr. Joker".
  • Issue 173 of World's Finest Comics had a story titled "The Jekyll-Hyde Heroes" where a scientist named Dr. Aaron give Batman and Superman a potion that caused them to respectively transform into copies of their respective enemies Two-Face and Kralik (an obscure Silver Age Superman villain).
• Green Lantern:
  • Kyle Rayner's vast powers were not being fully harnessed, so they formed a shadow entity called Oblivion in Green Lantern: Circle of Fire.
  • In Green Lantern: Rebirth, Hal Jordan's conjured body was warping between Spectre, the white-templed Evil Hal run by the fear entity Parallax, which is what he looked like when he did the genocide thing, and his own mixed-up personality, which looks like he did when he was a spry young pilot and at the top of his superheroing game. Often the head and shoulders of one entity will come thrusting out of one of the others. Specter only possessed Hal hoping he could purge Parallax, but now it looks like Parallax might just be getting the Specter's considerable powers, and the Specter and Hal can't see eye-to-eye enough to work well together.
• The original Eclipso had Bruce Gordon at war with his evil alter-ego, Eclipso. Later retconned with Eclipso being a separate entity trapped in a black diamond that possesses his user.
• In All-Star Comics #20, the JSA are helping industrialist Jason L. Rogers track down a criminal known as "The Monster", a hideous-looking man who follows Rogers around and has cost him his family and his business. It turns out that Rogers himself turns into "The Monster" and never knew it.

Marvel

• The Incredible Hulk: Bruce Banner and his more famous dark side the Hulk. This has been played with many times over the years, with Hulk varying from a brutal monster to an innocent savage. For a while between World War Hulk and Indestructible Hulk, Banner was portrayed as Hulk's dark side, since unlike Hulk, he'd actually killed someone. And in the Marvel 1602 Elseworld, David Banner gets transformed into the Incredible Hulk. Lord Banner works as an enforcer for James VI of Scotland and I of England, and is evil, sadistic and altogether not a nice bloke at all. Follow-ups reveal that the Hulk, on the other hand, is noble and intelligent. (And his influence eventually redeems Banner.)
• Spider-Man:
  • The Green Goblin is sometimes, and to an extent originally, depicted as a split personality of the milquetoast scientist Norman Osborn. The main difference is that Osborn is a Manipulative Bastard, while the Goblin is an Ax-Crazy psychopath. Since he came Back from the Dead, Osborn had been more or less in control and became the Goblin willingly and for shitz and giggles, but recently he's started losing it again. When he had a breakdown at the end of Dark Reign after being (to the public) the squeaky clean Iron Patriot, when they took his mask off he had Green Goblin paint on underneath... (though in that case, that might have been triggered by Nate Grey, who'd planned to cut the Goblin persona loose from deep within Osborn and show the world what he really was. While Nate lost that round, it looks like he won the war).
  • Speaking of Spider-Man villains, The Lizard, aka Curt Connors, also counts.
  • As does Mister Negative and his alter ego Martin Lee.
• In X-Men, Sauron (no, not THAT Sauron) has this kind of relationship with his alter-ego, Karl Lykos.
• In Daredevil, Typhoid Mary is the second, villainous personality of the otherwise nice and peaceful Mary Walker. She also has the downright psychotic Bloody Mary personality.
• Alpha Flight's Aurora switched between a free-spirited superhero personality and that of a highly repressed Catholic school teacher.
• The "A Murder in Paradise" Story Arc of Cable & Deadpool has Deadpool looking for the murderer of an Osama bin Laden-esque figure who took sanctuary in Cable's island country. Guess who did it and can't remember.

Other

• In Grendel, what starts out as Hunter Rose's supervillain identity gradually evolves into a sort of Mr. Hyde alter-ego, which jumps from host to host (or do the "hosts" just share the same psychosis?) over many generations. The Grendel persona best conforms to this trope with the third "host", Brian Li Sung, whose personal journal contrasts the guilt-ridden ponderings of Brian and the emerging rants of the Grendel within.
• The League of Extraordinary Gentlemen includes an aged, monstrous Hyde as a member. Jekyll is now thin and sickly while Hyde is a red-skinned, bulked-up giant monster, and it's implied that he was feeding off of Jekyll's energy. Hyde explains it by saying that "without me Jekyll has no drive, and without him I have no restraints."
• Mark Shaw aka Manhunter was constantly tracking a serial killer named Dumas: guess why he could never find him.
• In Mini Monsters we have Henrietta (The original and good entity) and Miss Hit (The Kick-Ass identity). Her father can also count.
• The Monster in My Pocket comic book featured Dr. Jekyll (the comic's interpretation of the "Mad Scientist" figurine in the toyline) as a member of the good monsters, with the evil monsters' leader Warlock once attempting to bring Jekyll to his side by force-feeding him the potion that turns him into Mr. Hyde and the good monsters' leader Vampire dreading that Warlock and his minions will be unbeatable with just one more monster on their side.
• The Zenescope horror comic Grimm Tales of Terror featured a Jekyll and Hyde story as its first issue of its second volume. A bullied nerd creates a serum that turns him into a more hunky alter ego. The twist is that the original "Jekyll" turns out to be the evil one.

Comic Strips

• In Scary Gary, Dr. Jekyll is Leopold’s doctor. As Jekyll he is a normal looking man, but when he turns into Hyde, he turns roughly 8 feet tall and green, gains a somewhat disfigured face and disheveled hair, has a much more threatening demeanor, and just makes strange grunting sounds instead of talking.

Fan Works

• In Origins, a Mass Effect/Star Wars/Borderlands/Halo Massive Multiplayer Crossover, Sarah develops into a downplayed version of this. She wasn't ever meant to have a personality, but when her controls are removed she manifests a helpful side and a Drunk on the Dark Side personality that tries to tempt her back into her old ways.
• In God Save the Esteem, this trope gradually comes into play. At first, Stacy Rowe, a wallflower high school student whose friends in the Fashion Club are so exhausting to put up with that Stacy gives hanging out with the local group of punks a try, albeit under disguise. But then she grows lonely and weary of trying to find a boyfriend who lives up to either group's standards, so she creates another identity as a nerd. Where this trope comes in is when she loses her grip on her personalities, and begins switching between them without control, and begins blacking out on what the other personalities did. By the time the fic ends she's up to five personalities: Extreme Doormat Fashion Club member, violent and alcohol loving punk, perky and upbeat nerdy girl with a stable relationship, paintball gun wielding vigilante, and British soccer team member. Following the timeline of the fic, she was only in control for a few months before she began switching at random. This doesn't end well for her when she snaps and switches rapidly through the whole roster of personalities at school...
• In The Merry Killers, Shinobu Maehara remains the sweet and friendly girl from canon unless she's wears red. Then she turns into Red, a Psycho for Hire assassin who can scare even the other Hinata Sou residents. Shinobu also uses a mirror lined with red tape to communicate wither her other self.
• The Secret Return of Alex Mack: As per canon, getting doused with GC-Divide causes you to split into a "good" and "bad" version of yourself. Alex uses it on Danielle Atron and then leaves her to fight the "good" version of herself — which wins the fight and kills the evil Danielle, effectively becoming an unusual sort of Heel–Face Turn.
• Ichinodō Shichido of Tales of the Undiscovered Swords whose Jekyll is polite, full of moral conviction and determination to distance himself from his ugly background as a Muramasa sword owned by a murderous master and Hyde is sadistic, twisted and calls the Jekyll's side's efforts to resist murderous temptations "delusional".
• As a result of a spell in You Call That a Costume?, Pinkie turns into her alter-ego, Pinkamena, because she was dressed as Mr Hyde. Downplayed with Twilight in that although she has to struggle not to lose herself to Midnight Sparkle, she is still in control of her Midnight Sparkle form.
• Tales of Sonic the Hedgehog: Robotnik describes himself as the Hyde to Julian's Jekyll, which the author confirms in the post-chapter note. As explained, Julian always had darker desires like a thirst for power and wanting to Take Over the World; the ROCC explosion just released him from his inhibitions and restraint. Everything Julian Kintobor fantasized about and kept under control, Dr. Robotnik does the instant it occurs to him.
• Ere we go, Pluz Ultra!: Izuku's Quirk has given him the mentality and personality of an Ork. When Aizawa erases his Quirk, Izuku's back to being a nervous stuttering mess.
• Tony Tony Chopper creates this dynamic in himself in the fanfic This Bites!. After doing research in Alabasta, Chopper created an enzyme to drastically increase his intelligence to gain the full potential of the Human-Human Fruit. Unfortunately, the increase in intelligence came with an equal decrease in morality and impulse control. Now Chopper often slips into a full-on Mad Scientist all too eager to vivisect his own teammates to learn what he can For Science!. It normally takes a Tap on the Head to force Chopper back into his normal mentality, though he has been training to overcome his inner Hyde himself.
• The Rapture Falls series gives Fontaine and Atlas this sort of dynamic (caused by Fontaine's splicing with exceptionally pure ADAM), though with the twist that the original personality (Fontaine) was the evil one, and the one created by the drug (Atlas) was his repressed good side.

Films — Animation

• In Scooby-Doo! and the Reluctant Werewolf, one of the monster racers was a spoof of Dr. Jekyll and Mr. Hyde in the form of a mild-mannered gentleman named Dr. Jackal who repeatedly and involuntarily transformed into a hideous lunatic named Mr. Snide.

Films — Live-Action

• The Adult Version of Jekyll and Hide: Somewhat different here in that both Jekyll and Hyde (Leeder and Hide) are homicidal.
• A major twist in Atlantics. Detective Issa is hell-bend on catching Souleiman, and convinced he's around and responsible for all the fires. It turns out that Issa's fainting spells result in him being possessed by Souleiman's ghost, and that he is unknowingly responsible for all the crimes he's investigating.
• The Amicus Productions version, I, Monster, followed the original novel quite closely but changed the characters' names in the hope of catching the viewers by surprise.
• The protagonist and Tyler Durden from Fight Club. Lampshaded by Marla: "You're Dr. Jekyll and Mr. Jackass."
• Dr. Jekyll & Ms. Hyde, itself a Comedic Remake of the darker Doctor Jekyll and Sister Hyde, parodies the trope, with meek scientist Richard Jacks turning into a lustful, cutthroat female alter ego named Helen Hyde via a recreation of his ancestor Henry Jekyll's formula.
• Me, Myself & Irene had this with Jim Carrey playing two guys in one — nice cop Charlie and bad cop Hank.
• Repo! The Genetic Opera has Nathan, doting father by day, Repo Man by night.
• Norman Bates and his mother in Psycho. Only spoilered because Alfred Hitchcock doesn't want us to spoil the movie for others.
• David Callaway and Charlie in Hide and Seek.
• The Little Stranger has a variation. The colleague of protagonist Dr. Faraday speculates that the hauntings at Hundreds Hall are a Jekyll-and-Hyde situation, with a shadow self fractured off from someone's worst impulses causing all the misfortunes. He is correct; Faraday's anger and resentment have been manifesting as a malevolent poltergeist, with its own separate lifelike body.
• The Two Faces of Dr. Jekyll has an interesting variation. Dr. Jekyll is hirsute, unkempt, ill-tempered and mannerless; Hyde is clean-shaven, well-dressed, well-mannered, and charming. But Jekyll's still a decent guy, and Hyde is thoroughly depraved and evil.
• Bigger Than Life shows the schoolteacher Ed Avery (James Mason) abusing his prescription medication and going from an overworked frustrated teacher and husband to a psychopathic and abusive father, with an authoritarian attitude to teaching children. It's implied in the film that these attitudes and feelings were within him all along but the drug simply provided an outlet.
• Julius Kelp in The Nutty Professor (1963) (Sherman Klump in the remake) and his alter ego Buddy Love are a more family-friendly variant; Kelp/Klump is a nebbish with virtually no social graces, while Buddy Love is a casanova who oozes charisma.
• Jekyll And Hyde Together Again had Mark Blankfield going from humble doctor to drugged-out sex-crazed swinger.
• In the original Total Recall (1990), Quaid is actually an implanted personality of the villain Hauser. Maybe.
• Before I Hang: After taking the age-reversal serum, Dr. Garth is occasionally overcome by a sudden urge to kill induced by the presence of an executed murderer's blood in his system. Garth does not remember committing these murders.
• In Citizen Kane, Charles Foster Kane tells Thatcher early on, "The trouble is, you don't realize that you're talking to two people," referring to himself as both a man of wealth and as a man of the people. One of the main points of the movie is the internal war between those two sides. It can be argued that both sides lose by the end of the movie.
• Nick and Francois in Youth in Revolt.
• Other Halves is about an dating app that manifests and then unleashes the user's "other half," or id.
• The underrated 1970 film The Man Who Haunted Himself. Rather than one character (played by Roger Moore) manifesting two personalities, there are two Roger Moore's running around, with the Hyde character gradually taking over the Jekyll character's life until he's the one assumed to be the imposter.
• Persona (1966): The dynamic between Elisabet and Sister Alma; the strange scenes in which one turns the other's head towards her; the reaction of Mr Vogler to Anna.
• Sexual Chemistry: Our hero doctor is trying to develop a drug to increase libido, and gets more than he bargained for. This one differs in that his new alter ego isn't evil.
• Split: Kevin has 24 personalities. They range the gamut from extroverted fashion designer Barry to Central Asian history buff Orwell to the kidnapping Dennis to The Beast who combines animalistic strength and an insane ideology about suffering.

Literature

• The Strange Case of Dr. Jekyll and Mr. Hyde, which is the Trope Namer, gives us the unbuilt variant of this dynamic. Henry Jekyll is a good man with evil urges who deliberately created a potion to turn himself into Edward Hyde for a selfish purpose and, up until a murder was committed, derived pleasure from his darker self's actions. However, eventually he started changing even without the potion, and had to create a new one to ward off Hyde taking control. Recreating the formula proved impossible, and he wrote a letter to explain everything before dying. The idea of Jekyll and Hyde being the same individual was originally a Twist Ending; the reason for almost all adaptations removing this aspect is that the twist eventually became well-known.
• Tyler Durden and the narrator in Fight Club, though you probably know this already.
• The Novelization of Halloween (1978) claims a case of this to be the motive for The Shape's killing spree, with Michael as the "Jekyll" and Enda as the "Hyde".
• Smeagol and Gollum in The Lord of the Rings.
• In Neil Gaiman's American Gods it is revealed at the end and hinted throughout that the paired Slavic gods Czernobog (which translates to Black God) and Bielebog (White God) are a Jekyll and Hyde.
• In the book version of Dexter, the lovable Serial Killer is motivated to kill by a sort of being/other personality, the Dark Passenger.
• In the Xanth book Crewel Lye, there's a Magician named Yin Yang who spends a lengthy amount of time pretending to be two different people, Yin and Yang, who were having a competition to see which one should be heir to the current King. It turns out that the competition was about which side of his personality should take over.
• Nabokov's Lolita has the whole dynamic between Humbert and Quilty leading to the frankly quite trippy scenes at the end, the chase, and especially the murder.
• Odetta and Detta in The Dark Tower.
• In Skulduggery Pleasant, there's Darquesse for Valkyrie and Lord Vile for Skulduggery.
• Jekyll's transformation is inverted and averted by Julian Advent of the Nightside series, who faced the same choice as Jekyll when he discovered a similar formula, but chose to drink the version that brought his Good side to the fore, making him The Cape instead of this trope.
• Eden Green's needle-humans often develop darker 'backup' personalities in order to deal with the horror-show their bodies have become.
• "A Drug on the Market" by Kim Newman is about what happens when a consortium sells Jekyll's formula commercially. Among the test subjects is a clergyman who becomes a loose woman and an anarchist whose "dark side" runs off to get an office job.
• In the second Welkin Weasels trilogy, the mild-mannered gerbil Professor Speckle Jyde takes a potion to become the rude and belligerent shrew Lycus Heck. In this case, Jyde is well aware of the potion's effects, and believes taking an occasional holiday from being polite and mild mannered is probably healthy.
• The third book of the Extreme Monsters book series, Meet Mr. Hydeous, introduced Doc's nephew Gerald, who had little interest in extreme sports. Gerald ends up drinking a potion that turns him into Mr. Hydeous and his alter ego starts competing against the Extreme Monsters by joining Team Pendant.
• In the short story "The Strange Case of Dr Sacker and Mr Hope" by James Lovegrove, Jekyll never tries the formula himself. Instead it is taken by Sherlock Holmes, who believes it to be the "good" formula, that will rid him of all the negative emotions that get in the way of being a detective. This doesn't work out for him.
• A Scanner Darkly has the main character hunting down a drug dealer who is in fact himself, having developed split personalities from the drug.
• The Jekyll Legacy (by Robert Bloch and Andre Norton): The plot revolves around Hester Lane discovering she's really the niece of the missing (actually deceased) Dr. Henry Jekyll, right around the time that a handful of murders similar to one Hyde committed are happening. It turns out to be someone who's been using Jekyll's formula to become their own "Mr. Hyde", though unlike the original Jekyll, this person took the potion by accident and now delights in their evil rather than being ashamed of it.
• In Please Don't Tell My Parents You Believe Her the retired supervillain First Horseman theorizes the main character, Penny, had a mild case of splitting into a mildly villainous personality called "Bad Penny" who a mind-reader confirms is almost the same as Penny.

Live-Action TV

• Ace Lightning has Random Virus, who has two personalities, good and evil, signified by his cyborg eye being green or red, respectively. He doesn't seem to have much control over whether he's good or evil, although Ace managed to turn him good temporarily by reminding him that he was a Lightning Knight, and therefore a 'good guy'.
• Hal from Being Human (UK) appears to be this with his vampire side. Strange, seeing as neither Mitchell nor Adam appeared to be this, and Hal has drunk blood without going full Hyde. It's implied that this is because of his continuous, long-running suppression of his vampire instincts, having lasted about fifty-five years longer than either, as the longest either of them has gone straight is a few months.
• On The Big Bang Theory, after Penny wakes up with Raj, she refers to herself as Dr. Jekyll and Miss Whore.
• Playing this trope painfully straight is Darkstrike from Birds of Prey (2002): he's a vigilante hunting the Creeper, the Serial Killer who killed his girlfriend.
• Buffy the Vampire Slayer:
  • The Big Bad of Season 5 is Glory, a female Physical God imprisoned within the body of Ben, a male human. Although Glory is the more powerful personality, Ben is still able to hamper her to some degree. In the season finale, the distinction between them starts to break down, with Glory beginning to feel genuine human emotions (like sympathy, guilt, and fear) and Ben becoming more callous and self-serving (like being willing to cooperate with Glory's plan in order to survive himself). Eventually they are able to switch back and forth rapid enough to actually talk to each other.
  • More obvious, Angel and Angelus from Buffy the Vampire Slayer and Angel. Though at different times in both series that varies between Jekyll & Hyde and Enemy Within. It all depends on whether Angel simply becomes evil when he loses his soul (as his Buffy appearances and Angel's fifth season implied) or if losing his soul replaces Angel with the demon soul of Angelus (as it seemed to be in Angel's fourth season). Except that Angel losing his soul always leads to the demon Angelus taking over, because Angelus is always there. Otherwise Angel would, at least, not be able to vamp out, and probably keel over dead, being a corpse, without the demon animating him. For proof, see the season 2 finale of Angel. When he tries to vamp out on Pylea, the demon takes over completely and is a mindless, inhuman monster. Angelus, particularly according to that example, is a blend of the demon's personality and sadism with Angel's memories and brain (but not his soul). When Angel loses his soul, it's gone, and all that's left is Angelus. All of those incidents where he's evil are Angelus.
  • There's also the Series Three episode "Beauty and the Beasts", which features a high school student drinking a chemical potion that turns him into a literal monster who abuses his girlfriend and attacks anyone who gets too close to her. Subverted in that it was revealed by the end of the episode that the potion didn't actually change his personality, it was just an excuse and he was really that heinous, and after using the potion for long enough he didn't even need it in order to transform anymore.
• Season 6 of Dexter has Travis and Professor Gellar turning out to be just one person, they even try to Sixth Sense the twist for nine episodes. It was painfully obvious.
• The main hook of Do No Harm: The title character is an ethical doctor who switches to a malevolent second personality at 8:25 pm each night and then reverts back at 8:25 am the following morning. After keeping this personality sedated with drugs for years, one day he finds that his body has become immune to them... Unleashing the other personalty, now bent on destroying his life. Subverted in the series finale when it was revealed that the benevolent personality was in fact the actual alter while the malevolent one was the original.
• Doctor Who:
  • Used with all the homages to the Universal Horror version of the story with Sorenson in "Planet of Evil", whose addiction to antimatter repeatedly transforms him into a monster.
• In The Dukes of Hazzard, Luke inadvertently ingests a mind-altering serum. At first he's just snarky and testy to his cousins, but soon becomes despicably evil, terrorizing Hazzard, robbing the bank, disrespecting Uncle Jesse, and even becoming a masher.
• In the original live-action series of The Ghost Busters, the ghost of Dr. Jekyll is one of the ghosts the Busters deal with as he materializes in the castle trying to cure himself of Hyde. Interestingly, Hyde is rendered as a separate entity from Jekyll, taking the form of an obnoxious man in a caveman outfit.
• The Imperfects: Gender-Inverted. Isabel Finch is a manifestation of Dr. Burke's Id.
• Iron Fist (2017): The second season introduces Mary Walker, a slightly more realistic version of Marvel's Typhoid Mary from their comics. This version is a former special forces soldier and PTSD sufferer with a raging case of Hollywood dissociative identity disorder; "Mary" is a mild-mannered, fragile woman, while the amoral "Walker" has the military skills, being an effective mercenary despite her mental issues, able to take on the wielder of the Iron Fist with some smart planning and the right weapons. Then at the end of the season they both realize there's a third, even more dangerous persona, born from the incident that caused their DID in the first place that neither of them knew about.
• Jekyll plays around with the dichotomy. For the first half of the series Jackman ruins his life trying to minimize the damage Hyde could cause, particularly to his own family. Although Hyde is meant to be the most intelligent creature on the planet, his immature mind and Jackman's own substantial intelligence and careful planning allow Jackman to keep a tight hold on Hyde's actions.
• Jekyll and Hyde (2015) has Robert Jekyll, grandson of the infamous Dr. Jekyll, and his alternate personality, Hyde. In this Hyde emerges when Jekyll doesn't take certain drugs.
• Julia Jekyll and Harriet Hyde had the main character Julia Jekyll turn into a hairy monster called Harriet Hyde uncontrollably.
• Kamen Rider:
  • Kamen Rider Den-O effectively has four Hydes, sometimes even five, courtesy of the Imagin that live on his time-traveling train and need to possess his body in order to interact with the outside world. Each one gives Ryotaro a radically different personality and appearance whenever they take control, although they're all played by the same actor. They're also all heroes, albeit sometimes of questionable effectiveness.
  • Kamen Rider Fourze: The Cygnus Zodiarts develops a split personality upon using his Switch for the first time, his meek cosplay otaku persona suppressed by a vain Dark Messiah. The Gemini Switch has a similar effect.
  • Kamen Rider Wizard: Wiseman, leader of the Phantoms, and the White Wizard appear to have this relationship. It's subverted when it's revealed that the Wizard was always in complete control and was simply using his monstrous alter-ego to play both sides.
  • Kamen Rider Ex-Aid: The title character flips between his normal identity of caring doctor Hojo Emu and the brash, confident Genius Gamer M whenever he transforms, with an early upgrade allowing them to split into two bodies to become Ex-Aid at the same time. Both are equally heroic, until much later in the show when it comes out that "M" is actually Emu's Enemy Without Parado.
  • Kamen Rider Revice: Daiji Igarashi/Kamen Rider Live and Kagero/Kamen Rider Evil are a straight example, with their shared Driver changing forms to match whichever one is in control. Daiji eventually manages to kill Kagero, but in this case Jekyll on his own turns out to be much worse than Hyde.
• Moon Knight (2022): From the start of the series, Marc Spector (and his secret identity, Moon Knight) and Steven Grant (and his secret identity, Mr. Knight) are shown as alternate personalities of someone with raging DID. (Initially, Marc knows about Steven, but not vice-versa.) Neither is technically a dark "Hyde", though; Marc is fully capable of competent violence, unlike the mild-mannered pacifist Steven, but retains a working sense of morality. However, it becomes increasingly clear through the series that there may be a third persona. This is eventually revealed to be the ruthlessly violent Jake Lockley, who emerges when even Marc can't handle a threat and usually solves it by killing everyone within reach.
• Mouse (2021) plays with this. After a Brain Transplant Ba-reum ends up with part of Yo-han's brain. All the evidence suggests Yo-han was a serial killer, so when Ba-reum starts having flashbacks to murders he assumes Yo-han's personality is still alive in his brain. Actually Ba-reum was the killer and Yo-han was innocent, so Ba-reum's original personality is the "Hyde" and Yo-han is the "Jekyll".
• In the Murdoch Mysteries episode "Excitable Chap", a mysterious Lurker begins not-exactly-terrorising ladies at the same time as James Pendrick is developing his new brain-enhancement drug. It inevitably turns out that state of unconsciousness he enters after his period of frenzied work is actually him acting out his subconscious desires as the Lurker. When the Lurker seemingly kills someone, Julia points out that if Pendrick isn't a natural killer, his Lurker wouldn't have murder in him either. It turns out someone else has been taking the drug.
• A show called My Own Worst Enemy features a man leading a double life. His normal side is Henry and his alternate ego (that he doesn't know about) is the spy Edward, which is most likely an allusion to the original Dr. Henry Jekyll and Edward Hyde. Reverses the usual Jekyll/Hyde dynamic in that Edward is the original personality; Henry is a construct. While Edward is the edgier of the two personalities, he's not actually evil.
• Once Upon a Time features the actual Dr Jekyll and Mr Hyde in Season 6. As is typical Hyde is brutal, violent and inhumanly strong; while Jekyll is intellectual, meek and nervous. Hyde is part of a Big Bad Duumvirate with the Evil Queen and was the iron-fisted dictator of the Land of Untold Stories. In a twist it's revealed that he was originally the more moral of the two, and was actually a manifestation of Jekyll's passion rather than his dark side. He became more malevolent after Jekyll murdered the woman they both loved when she chose Hyde and framed him for the killing.
• In The Outer Limits (1963) episode "Expanding Human", a consciousness-expanding drug transforms one of its researchers physically and mentally, turning him back and forth between his normal self and a super-strong, super-intelligent alter ego who wants to Take Over the World and convert or destroy the rest of humanity.
• Power Rangers:
  • Mesogog and Anton Mercer from Power Rangers: Dino Thunder. Eventually Mesogog splits himself off from Mercer because he gets fed up with sharing. It frees the Rangers to not hold back against him, but he becomes even more effective due to being able to act more often and not just when he surfaces.
  • A similar example is the villains Heckyl and Snide from Power Rangers Dino Charge. Played with, however, in that both personalities are firmly evil, just preferring different methods and disdaining the other's. Towards the end, Heckyl has a Heel–Face Turn, and Snide uses some tech to completely separate them.
• Adam Worth from Sanctuary is said to be the in-universe explanation for the novel. Neither personality is particularly stronger, but unlike most examples, both sides work in tandem.
• Smallville:
  • Davis Bloome/Doomsday.
  • Before that, when Clark tried to explain himself to Chloe about not being himself lately (Lionel Luthor had swapped bodies with him), she stated that people sometimes act as Jekyll and then as Hyde but are the same after all.
• Star Trek:
  • In the Star Trek: The Original Series episode "The Enemy Within", a transporter malfunction splits Kirk's good and evil sides.
  • A brainwashed Geordi is used as an assassin in the Star Trek: The Next Generation episode "The Mind's Eye".
  • The Star Trek: Voyager episode "Darkling" has the Doctor develop a villainous split personality which he is unaware of as a result of making some unwise adjustments to his programming.
• Supernatural: Kind-and-gentle human Sammy, arrogant-and-violent demonic Sammy. And then there is soulless robo Sammy...
• The Vampire Diaries:
  • Stefan Salvatore. He has one side of his personality which is kind, caring, empathetic and compassionate and heroic ("Jekyll", Hero!Stefan) and another side of his personality which is sociopathic, crazy, addictive, cold and ruthless ("Hyde", Ripper!Stefan)
  • Alaric Saltzman is a better example. Normally a good-hearted vampire hunter, he develops a serial killer Hyde persona from dying too often.
• Where In Time Is Carmen Sandiego had a girl named Jacqueline Hyde, who jumped from sweet, innocent schoolgirl to raving, snarling harpy at the drop of a hat.

Music

• "Sacrifice" by Disturbed is about this trope, along with themes of "My other side is going to hurt you".
• "Mz. Hyde" by Halestorm invokes the trope, but it's actually about a someone who's decided that she's going to stop pretending to be a wholesome, good girl and get kinky in the bedroom.
• Mentioned in the chorus of the blink-182 song "Natives":
  They turn us loose in the night
  I'm fucking Jekyll and Hyde
• Five Finger Death Punch:
  • Their song "Jekyll and Hyde" is, unsurprisingly, about this trope.
    Oh, yo, yo, there's a demon inside!
    Oh, yo, yo, just like Jekyll and Hyde!
    Oh, yo, yo, all this anger inside!
    Oh, yo, yo, I feel like Jekyll and Hyde!
  • Also mentioned in "Welcome to the Circus" with the line "Everybody's got a Jekyll and Hyde."
• "Dr. Heckle and Mr. Jive" by Men at Work. Almost a straight-forward summation of the plot of The Nutty Professor.
• A variation can be heard in "Battle of Someone" by Blues Traveler. The first verse starts, "Well I love no one," and is generally cynical and embittered. The second verse starts, "Well I love everyone," and is idealistic and hopeful. The final verse contains the line "The preceding verses are the halves of my soul," and describes how the singer recognizes the battle within him between the darker and lighter sides of his being.
• The first 5 Albums of ASP tell the story of the Black Butterfly, a vampire-like entity, which sometimes seems to inhabit the body of the protagonist. For example, in the song Lykanthropie (Es tobt ein Krieg in mir), it's compared to werewolves, with the protagonist not remembering what he did while under the creatures influence. Also, in promotional shots, both the protagonist and the Black Butterfly are represented by the bands lead singer Alexander Spreng.
• Played with in "Bubba Hyde" by Diamond Rio. The song is about an ordinary guy named Barney Jekyll, a grocery store employee and volunteer firefighter who seems like an unhip ordinary man, except on Friday nights, when he dons a leather jacket and zebra boots, and becomes the party animal "Bubba Hyde".
• "Me And I" by ABBA directly invokes this trope: "Part of me is acting while the other stands beside/Yes, I am to myself what Jekyll must have been to Hyde..."
• While it's not the primary way that Eminem portrays Slim Shady, he's sometimes imagined as this:
  • In Slim Shady EP, Slim is presented as the split personality of Eminem ^note which we'd now understand as being the split personality of Marshall - Eminem hadn't figured out the triune Marshall-Eminem-Slim Kayfabe Music personas yet, and still saw "Eminem" and "Marshall" as the same character, complete with a shoutout to Jekyll and Hyde in "Low Down, Dirty":
    Wearing visors, sunglasses and disguises
    'Cause my split personality is having an identity crisis
    I'm Dr. Hyde and Mr. Jekyll...
  • In the unreleased song "Angry Blonde" (intended for The Marshall Mathers LP), Slim Shady would have been represented as a rage-induced physical transformation - "you wouldn't like me when I'm angry - the Reeboks on my feet turn to Nike, and my skin pales, hair turns blond..."
  • The concept of Eminem's Horrorcore album Relapse is that when Marshall Mathers takes drugs, he becomes Slim Shady and starts stalking and murdering people.
  • In "Stronger Than I Was", the narrator describes their lover as 'Jekyll and Hyde' - one of the many reasons fans interpret the song as being from the perspective of Kim, Eminem's ex-wife and constant lyrical punchbag.

Puppet Shows

• Mr. Meaty: After years of being showered with insults without getting mad (he chugs them deep inside), Parker finally explodes when a client insults his ribs specialty. The pent-up emotions turn him into a purple, Mr. Hyde monster called Incredible Jerk that throws hurtful insults left and right. Parker reverts back to normal when he's let off enough steam, but transforms against whenever anyone insults him again.

Radio

• John Finnemore's Souvenir Programme: Series 1, Episode 3 includes a sketch consisting of Jekyll and Hyde writing letters to one another: Hyde is constantly sabotaging Jekyll's equipment, food, and moustache (and killing costermongers), and Jekyll is telling him off. Eventually, Jekyll teaches Hyde his place by threatening to subject him to a vasectomy. Hyde meekly apologizes to him and promises not to torment Jekyll again. He can still kill costermongers, though.
• Parodied in one sketch on Saturday Night Fry, in which hard-working Dr John Fordyce (Stephen Fry) discovers a serum that transforms him into supervillain Jenny Flamisto (Emma Thompson). He / she is opposed by Don McElwaine (Hugh Laurie), who uses the serum to change into Barry Cryer (Barry Cryer).

Tabletop Games

• Godforsaken: The moord's temperament depends on the elaborate movements of Korak-Mar's multitudinous tiny moons. 90 to 95 percent of the time, the moord live calm lives of subdued contemplation and careful, considered action, sleep fairly often, meditate at other times, and do not eat, mate or hunt. The rest of the time (called feasts), moord engage in revels of reckless abandon, hunt wild game with ferocity and bloodlust, eat voraciously, and engage in vigorous sex. However, the changes do not alter the overall ethics of the individual, only the chosen actions and responses to stimuli; a feasting moord becomes more fierce, uninhibited and barbaric, but not insane.
• Pathfinder: The Alchemist class can create a mutagenic potion that changes his/her personality and appearance, making the character more physically powerful at the expense of their mental abilities. The Master Chymist Prestige Class takes this a step further, allowing the alchemist to create a unique infusion that, when taken, changes the character's personality and Character Alignment and possibly gives them a monstrous appearance; the two personas have separate minds and may work against each other. That said, the Split Personality doesn't have to be evil, just a different alignment; a Lawful Good chymist could have a Chaotic Good alter ego, for instance.
• Magic: The Gathering, in its Gothic horror-themed Innistrad expansion, introduced "Civilized Scholar", a double-faced card that transforms into "Homicidal Brute". He was actually named "Jekyll and Hyde" as a placeholder in the early designs for the set.
• Ravenloft:
  • The quevari, a human subspecies from the setting, live as benign vegetarian pacifists by day, but are bloodthirsty killers by night.
  • The darklord of Nova Vaasa, Sir Tristan Hiregaard, struggles against his crime-lord alter ego Malken.
• Every character in Kindred of the East: the soul of an eastern vampire is divided into the higher Hun and the lower P'o. It is as troublesome as it sounds, but the P'o is indispensable. It serves as the Superpowered Evil Side, providing some essential combat powers (indeed, a vampire couldn't even grow fangs without it) and is responsible for him being undead in the first place.
• Kindred of the East draws on Wraith: The Oblivion: in death, the dark side of the living personality, the Shadow, becomes independent, developing its own personality, and can at times gain enough strength to assume control over the wraith. The inverse applies to Spectres, for whom the Shadow is the dominant personality; their light side, the Psyche, remains independent and can at times become strong enough to take control.
• A variant is possible in Aberrant. Novas can accumulate physical and/or psychological mutations from various sources (most of which give you power at this cost), and can gain the ability to suppress their superpowered side, including these mutations. Of course, there's no reason that this Superpowered Alter Ego has to be evil; it's just as likely to be heroic or villainous as is a "normal" person.
• The generic GURPS system has a “Split Personality” disadvantage to cover this sort of thing in general. GURPS Steampunk 2 includes a discussion of various ways to handle the situation from the trope-namer novel and later versions of that idea.

Theatre

• In the 1933 Broadway musical Pardon My English, a British Upper-Class Twit named Michael Bramleigh is unconscious of also being a notorious jewel thief called Golo. A Tap on the Head causes him to switch between the two identities and their respective love interests.

Toys

• Monster High:
  • Jackson Jekyll and Holt Hyde. Unsurprisingly, but somewhat subverted in that neither of them are evil. Jackson is a rather sweet, quiet, studious boy, whereas his alter ego is louder and more boisterous but still has a good heart. Granted, Holt Hyde is a monster, but considering the setting that is a compliment.
  • Jackson's own mother, Sydney, is also an example of this. She's only found in Jackson's journal and some of the books, but she still counts as one due to her being the daughter of the original Dr. Jekyll. Due to her inheriting the dual nature, Jackson gets it too. Likewise, she isn't evil either, but is described in the journal entry as appearing as her Hyde side when local monsters were teasing a then-five-year-old Jackson.
• SuperThings has the character Morph. His creation consisted of the mixing of a variety of essences, both hero and villain, forming the unstable blob. Due to having so many types of essences making his structure up, he has two personalities: his blue, white eyed Hero form, and his green, yellow-eyed Villain form. Unfortunately for himself, his powers are unstable to the point that he can't switch sides at will, nor does his Hero side or his Villain side realize either exists.

Video Games

• Batman: Arkham Knight: Harley Quinn's DLC story reveals her insanity to be this, with Harley Quinn being haunted by the voice of Dr. Harleen Quinzel. Harleen has no power over Harley, and is trying to get Harley to give up on her ramages and return to their normal life. Harley doesn't want to listen.
• Emil from Tales of Symphonia: Dawn of the New World has two personalities. First, there is his normal, timid, self-effacing personality. Then there's his "Ratatosk Mode," which is significantly more aggressive, to say the least.
• Xenogears: Fei, the player's character, and Id, the mysterious super-powerful lone villain.
• In Summon Night Swordcraft Story 2, one of your Guardian Beasts is a trashtalking demon who claims to have been possessed by her angelic sweet side. Subverted in the matter that the demon is the leading personality, with the angel being the hidden "Hyde".
• Kind of easy to miss, but Quest for Glory V had Praetorius and Mobius. While Praetorius is nicer than Mobius (which isn't all that hard), he's still completely okay with poisoning wizards in order to prove science superior. The character does change form when he's finally called out on this, but the graphics make it hard to tell, meaning the dialog is the only discernible indicator.
• Mewgenics A Jekyll is a bright-eyed, positively adorable kitty enemy. Give it a few turns and they'll morph into far more powerful (and uglier) Hydes.
• In the Neptunia series, CPUs are a mild example. While there's only one consciousness and they retain all their memories, goals, etc. during the voluntary transformation, their normal and Hard Disk Divinity forms can have very different personalities. Neptune's HDD form being a more mature Lady of War is one example. Another is Plutia, who goes from a friendly, scatterbrained girl to a stone-cold, ally-terrifying Dominatrix.
• In Bungo to Alchemist, the two Nakajima Atsushi share one body. Outer Atsushi is the calm, meek Gentleman Scholar 'Jekyll' more inclined to intellectual pursuits and social life, while Inner Atsushi is the proud, barsh Blood Knight 'Hyde' who only comes out for battles.
• In BioShock Infinite Booker and Comstock are the same person. In the beginning it's more of an Evil Twin situation - they do not actually "merge" like for example dead Chen Lin and living Chen Lin. Metaphorically, though, Comstock is the evil within Booker - both are single-minded, cynical and have a high capacity for violence. Booker is also willing to commit massive manslaughter and serve blatant lies to reach his goal (which in the beginning of the game is even quite morally corrupt). Later on, the metaphor becomes physical reality. Firstly, when Booker kills Comstock but is forced to take charge of the Hand of the Prophet and use the Songbird to destroy a Vox Populi attack. Temporarily, he is Comstock in both biology and social function. Secondly when he is transferred back in time to actually merge with the earlier version of himself that is set on the path of becoming Comstock. When this past Booker "remembers" his future actions as the Hyde, he chooses to let himself be killed. The hero has, indeed, "caught himself".
• It turns out that, in The Suffering and its sequel, whenever Torque transforms into a Malefactor, it's actually his second personality, Blackmore, coming to the forefront.
• Doshin, the kind, benevolent, helpful giant, and Jashin, the evil, sadistic, vicious version, in Doshin the Giant.
• The very uptight Berio in Duel Savior Destiny has an exhibitionist kleptomaniac side in Black Papillon that she developed as a way of dealing with stress. While Berio is highly disapproving of how her other side reacts and seems unaware, deep down she knows that it's probably her.
• Borderlands 2 has Krieg, who is split between the dominant, psychotic personality and a subdued sane personality. The latter tries to ensure that the former only kills "the deserving" and even swears that if the latter ever sheds innocent blood that it'll take over and commit suicide. In response, the psycho personality will even bash himself in the face with his axe to silence the voice.
• In the iOS game Layton Brothers: Mystery Room, Alfendi is in this predicament thanks to an incident 4 years ago. However, it seems that the "Hyde" is the real personality while his new persona is the Jekyll.
• In Metal Gear Ac!d, Solid Snake realises he knows a lot more about the facility than he expected. It's explained to him that he took the alias "Hans Davis" to perform some hideously unethical experiments on psychic children, and through repressing his memory of these events and of all the other terrible things he's done in his life, the ruthless and evil Hans has become an alternate personality into which he occasionally switches or even hallucinates conversing with. This is eventually revealed to all be the result of psychic Gaslighting.
• The Ultimate Haunted House has Gahan Wilson, the ghost host of the mansion, suffering from a Split Personality due to a formula he drank, splitting him into a good and evil side. The good one will give hints and items to the player. The bad one will curse the player, steal items, or summon monsters into the room. Part of the challenge of the game is determining whether Gahan is good or evil at any particular moment, especially considering Evil Gahan will pretend to be Good Gahan in order to lure you into a false sense of security.
• The Closer: Game of the Year Edition has @twitter, the personification of the social media network. One moment, it's cordial and pleasant (albeit a bit obsessed with #Monetization). But once the trolls have their way, it involuntarily starts throwing out curses, slurs and other unpleasantries. Naturally, it has issues with its predicament.
  @twitter: This [The Altar of Needless Cursing in the Gritty Reboot world] reminds me of the time I tried to ban the #word "fuck" in #hashtags.
  The Closer: You tried to ban "fuck"?
  @twitter: Yeah, it didn't go #well. (trolls take over) FUCKFUCKFUCKFUCKFUCKFUCKFUCKFUCK #FUCKFUCKFUCKFUCKFUCKFUCKFUCK (@twitter reins the trolls back in) That is basically what the #trolls did in response.
• In Dishonored 2, Alexandria Hypatia is a saintly doctor desperately trying to find a cure for a disease that's running rampant through Karnaca's silver miners. So desperate, in fact, that she wound up testing one of her serums on herself, inadvertently creating Grim Alex, an Ax-Crazy cannibalistic serial killer.
• Dead In Vinland has one that comes as a shock reveal: gentle, helpful, devoutly religious Brother Angelico has been having dissociative blackouts for most of his life in which he becomes an Ax-Crazy Serial Killer and then flogs himself with a whip, crying about "the demon." It's left Maybe Magic, Maybe Mundane whether it really is a demon; the player can choose to kill him, exile him, or find a way to cure him.
• Five Nights at Freddy's:
  • It's implied that this is how Glitchtrap's brainwashing possibly works. Luis notes in one of Five Nights at Freddy's AR: Special Delivery's unintended emails that there appears to be two sides to Vanessa when it comes to her online activity: the Glurge Addict who loves nature, and the Nightmare Fuel Station Attendant who is interested in Cold-Blooded Torture. Similarly, in Five Nights at Freddy's: Security Breach Vanessa behaves differently depending on whether she's in her security guard persona or her rabbit mask persona; Vanessa normally is a grumpy Child Hater just trying to do her job, while Vanny is Faux Affably Evil and energetic. There's some indication in the notes that Vanessa may not entirely remember her actions as Vanny. The "Princess Quest" minigames also have puzzles involving the use of a 'shadow' version of the player character, further hinting at it.
  • The Daycare Attendant from Security Breach is an animatronic with two modes. The first one you're introduced to is themed around the sun and is friendly, if a little clingy and overbearing. It is more of an obstacle than a threat, as it just wants to play with Gregory, a child who went into the Daycare after hours. There is, however, one rule when visiting the Daycare that it emphasizes: keep the lights on. The reason why shortly becomes clear, as the Attendant transforms into a moon-themed mode that is a threat, as it chases Gregory around the Daycare while muttering about how 'naughty children' need to be punished for being up past their bedtime. One note that can be found in the area reveals it has traumatized at least one child with this sort of behavior before. Needless to say, Sun is terrified of Moon and immediately kicks Gregory out once it reverts back. The 'Ruin' DLC introduces a third mode, Eclipse, which is implied to be a mixture of Sun's and Moon's positive traits.

Visual Novels

• ChronoBox: All test subjects have an evil personality in their head that threatens to take over and cause chaos in the world, that's why Tsuzurai with an insist of the government started working in Eden, curing those students.
• Toko Fukawa of Danganronpa: Trigger Happy Havoc has a split personality that happens to be an infamous serial killer known as Genocide Jack, whom she can summon by tasing herself.
• Jekyll & Hyde (MazM) is pretty faithful to the source material save for Mr. Hyde being a little more Bishōnen than strictly necessary. To be fair to the artist, he is never described as ugly in the book, just creepy and deep in the Uncanny Valley, and those aspects of his character come across just fine.
• Angel Starr from Phoenix Wright: Ace Attorney, complete with bangs moving from one eye to another depending on whether she's sweet or sour.
• Tohno Shiki from Tsukihime; when either his life is in extreme danger or he is confronted with something non-human he loses grip on his consciousness and becomes the amoral sociopathic killer Nanaya Shiki, who is a highly skilled assassin. Slightly subverted, though, in that despite being the main personality, Tohno Shiki is the false, created identity while Nanaya Shiki is the 'original' (yet Nanaya rarely ever appears). Nanaya is the Shiki who would have been, had his clan not been wiped out during his childhood and him hypnotized and brainwashed later on into becoming Tohno Shiki.

Webcomics

• Anna and Susan in Sire. Indeed, they obsess over the original Stevenson work, and are even descended from Edward Hyde.
• It seems that Ples Tibenoch of Tess Stone's Hanna Is Not a Boy's Name has a Jekyll and Hyde disorder of sorts.
• Homestuck:
  • When Gamzee Makara is stoned, he's one of the sweetest, most goofy Love Freak characters in the whole thing. But when he gets sober...
  • Calliope and her "brother" share a body, and switch places whenever one goes to sleep or hears the other's name. Calliope is one of the sweetest and most helpful people the Post-Scratch Kids have. Her brother, on the other hand... This is actually normal for their species.
• Bram & Vlad has Henry E. Jekyll and his counterpart, Jack Hyde. You can tell them apart because Hyde is a violent thug with red eyes, sharp teeth, sharp nails and he supports Argentina during the World Cup.
• Henry Jekyll and Edward Hyde again in The Glass Scientists. Jekyll is a polite socialite hiding a high school's worth of insecurities while Hyde is ever-smiling self-described "creature of the night".
• In the retelling of the classic story, MK's The Strange Case of Dr. Jekyll & Mr. Hyde. Jekyll is a law abiding sweetheart to a fault of the high society who constantly fears confrontation especially with the Carews making him prone to getting walked all over. Hyde is a cocky vagabond of the lower class who just takes what he wants even if it means committing theft and he is not above being a ruffian or openly defying the Carews. Unlike most depictions though, this one depicts Hyde as not being evil deep down and just wild and selfish.
• The Search For Henry Jekyll has Jekyll and Hyde, but also Dr. Lanyon, who gained a split personality when Hyde injected him with the same formula used to make him.
• Doctor Haggard and Lord Bunstable in Girl Genius, the result of a not-entirely-successful attempt to recreate the jaegerdraught. Subverted since Bunstable isn't evil (although if he stays in that form too long he becomes psychotic) and if it comes to that, Dr Haggard is a crotchety old man who loudly expresses his hatred of people for petty reasons.
• They are one (technically two) of the main characters in Nightmarish. Jekyll is a slightly self-centered Nice Guy who just wants to live as the castle's scientist, while Hyde is an Ax-Crazy, Self-Harming, Big Eater Sadist. They can communicate with each other via reflection or shadow. Oh, did we mention that they're also apparently a demon?
• In El Goonish Shive, Elliot's superheroine spell includes female alter ego forms for when he needs to transform out of the super form in public but can't go through his default form since that would reveal his identity. None of the forms make him evil but each one has a distinct personality that he can override if he concentrates.
• The Ettin in The Order of the Stick prequel story "How the Paladin Got His Scar" invokes this. The left head goes on a rampage while the right head pretends to speak reasonably and engage whatever it's attacking. This just serves to distract the target and make it easier to kill.

Web Original

• This is how Spoony and Dr. Insano are portrayed in the Channel Awesome anniversary special Kickassia. This is subject to Negative Continuity;To Boldly Flee had retconned this into an anomaly caused by the Plot Hole, in 'reality', Spoony and Insano are indeed two separate people.
• Flippy from Happy Tree Friends. He's usually sociable, sweet and friendly most of the time, but whenever he sees or hears something related to his war past, he goes into his evil state and brutally murders his friends, believing they are enemy soldiers.
• Necro Critic's sidekick, Devil Critic, is introduced in one of these plots. However, as a subversion, he turns out to just be Necro's brother filling in for him while he's in an energy drink induced coma.
• Alfred himself is a depressed, naïve dog while his alter ego Dictator Pickles threatens to enslave the world's populace. Though Lucifer, his other alter ego, appears closer to the Hyde archetype: appearing to want nothing other than to destroy kill, and rape.
• Gemma and the Bear is a non-villainous example Played for Laughs. Gemma is a nerdy, neurotic white woman who turns into a cheerful, extroverted, gay black man named Bear when she falls asleep. They can't interact directly but are aware of each other, with Bear fancying himself Gemma's protector. His attempts to be helpful mostly drive her nuts, and, in the first season finale bring the FBI to her doorstep.
• Venturian Tale: This or demonic possession appears to be the case with Johnny Ghost and Jimmy Casket.
• In Inanimate Insanity we have Yin-Yang, in which the sides go back and forth fighting each other constantly.
• This is a Parodied Trope in The Runaway Guys: A regular appearance at their annual Colosseum charity streams is Lord Dona'tor, who is basically Tom Fawkes in an eye-obscuring red bathrobe. He has an ominous maniacal laugh and refers to everyone else as 'Fool!' in his Evil Sounds Deep voice, but since all he does is issue hammy demands that people keep donating to the stream his malevolence should easily be contained.
• James Rolfe's Board James review series had him play a mild-mannered board game reviewer closer to his normal personality compared to The Angry Video Game Nerd, his more famous character. In one episode, they do a crossover that reveals AVGN is in fact Hyde to Board James' Jekyll, and his AVGN side takes over. Later episodes reveal the dynamic is actually inverted. While AVGN is a foul-mouthed Manchild, he does manage to have softer, more sympathetic moments. Board James, on the other hand, is revealed to be an Ax-Crazy Jigsaw-esque murderer known as the Hangman Killer who tortures others using board games for amusement. This also gets a Dramatic Irony nod in The Angry Video Game Nerd II: ASSimilation, where AVGN, after fighting off Board James as a mini-boss, claims he was psycho and was glad he's not him.

Western Animation

• Batman: The Animated Series added another variation to this in Two-Face in the final season - he'd established a third personality called "The Judge", who targeted Gotham's costumed villains, including Two-Face himself, who would Go Mad from the Revelation.
• Beetlejuice:
  • Beetlejuice's sentient car Doomie is ordinarily docile and amiable, but occasionally turns into a manic, werewolf-like vehicle called the Dragster of Doom.
  • The episode "Dr. Beetle And Mr. Juice" has B.J. creating a perfume that has a weird effect—it turns whoever applies it into their opposite personae. When it accidentally hits Lydia, she turns from being sweet and introverted into an obnoxious prank-playing biker. Beetlejuice is turned into a handsome and germophobic version of himself, which wears off the instant he starts bathing, and at the end of the episode has Mayor Maynot become a hippie who's happy to let Beetlejuice off the hook for once.
  • The episode "Beetlebones" began with Beetlejuice having his bicentennial checkup from a Neitherworld doctor who is a version of Dr. Jekyll and Mr. Hyde, with the difference of personalities being that Jekyll tries to patiently get Beetlejuice to cooperate and Hyde being irate and snappy when Beetlejuice chooses to not take the medical checkup seriously.
• In the Count Duckula episode "Doctor Goosewing and Mr. Duck", Von Goosewing invents a potion that reverses everyone's personality. He and Duckula become "wicious wampires", Igor becomes happy and loving and Nanny becomes a brainbox.
• Dexter's Laboratory: The episode "Monstrosi-Dee Dee" has Dee Dee consuming a contaminated apple and repeatedly turning into a monster and back. Dexter has no idea she is the monster stalking his laboratory, so he follows her advice (when she's human) on where to hide.
• The Fairly OddParents! episode "Nega-Timmy" had Timmy Turner wish that he did the opposite of what his parents told him to do. The way this wish ends up backfiring is that Mr. Turner tells his son to be good, which transforms Timmy into a fanged, top hat-wearing Enfant Terrible who attempts to use a laser to start a chain of events that will lead to the destruction of Dimmsdale. Timmy ultimately returns to normal after Mr. Turner tells Timmy to be as evil as he can be in response to Nega-Timmy swaying his dad to go along with his plan by promising that one of the results will be Dinkleburg's house getting obliterated.
• Friz Freleng was particularly fond of this trope, seeing the many cartoon installments he produced with this theme. And for two different animation studios, to boot — Warner Bros. and De Patie Freleng Enterprises.
  • Looney Tunes:
    • Hyde and Go Tweet: Dr. Jekyll creates a formula that turns him into the monstrous Mr. Hyde, Evil Laugh included. It's precisely in the bottle containing the formula that Tweety goes to hide from Sylvester, thus getting transformed into a deranged bird that's twice Sylvester's size. The cat, of course, has no idea Tweety is the monster, so when the latter changes back to normal, the former is still trying to eat him.
    • "Dr. Jerkyl's Hide": Effectively a remake of Freleng's "Tree for Two", only instead of Spike (renamed Alf here) being walloped by a panther, Sylvester hides in Dr. Jerkyl's laboratory while running away from the dogs where he drinks the formula and becomes a monster cat capable of beating up Alf.
    • "Hyde and Hare": Bugs Bunny convinces the man who always feeds him at the park to adopt him. The man, Dr. Jekyll, already verges on uncanny territory with his too-big head and small hands. However, when he drinks the red concoction he's prepared at his laboratory and that he's addicted to, he becomes a green, red-eyed monster with hairy limbs. Bugs Bunny doesn't realize Mr. Hyde's real identity until he transforms in front of him while trapped in a closet. Then Bugs goes to the lab and off-screen drinks the red concoction — when he returns to the park, he slowly changes into a monster and scares the elderly without understanding why.
  • The Pink Panther:
    • The Dogfather section: The episode "Watch The Birdie" is a Recycled Script of "Dr. Jerkyl's Hide" with the dog gang in the role of, well, the dogs and a yellow bird in Sylvester's role, i.e., drinking a weird liquid thinking it's soda while hiding from his pursuers.
    • The Inspector section: In the episode "Sicque! Sicque! Sicque!" , the Inspector and Sgt. Deux-Deux are called to investigate a mad scientist's laboratory. Sgt. Deux-Deux is The Fool and drinks a potion he finds in a beaker to calm his acid reflux because he believes it's water. Never mind the sick green color and the bubbles. It turns him into a monster that goes to torment the Inspector, who, of course, doesn't know it's Sgt. Deux-Deux.
    • The Pink Panther section: In "Pink Lightning", Dr. Jekyll fuels his malfunctioning car with the same pink jug he takes to transform into Mr. Hyde (he's transformed at the time). That same car is bought by the Pink Panther. When it stalls, it turns into a monstrous, super fast form that gets the Pink Panther in trouble with the police.
• Garfield and Friends did their own spin on the tale in both a Garfield segment and a U.S. Acres segment.
  • The U.S. Acres episode "Dr. Jekyll & Mr. Wade" began with Orson reading The Strange Case of Dr. Jekyll and Mr. Hyde to the others and has Wade accidentally hypnotized into turning into a hideous brute whenever he hears a bell ring.
  • The Garfield segment "Dr. Jekyll and Mr. Mouse" had Garfield tell a version of the story while waiting for his microwave dinner to finish cooking. Garfield's version has the twist of Dr. Jekyll testing his formula on a mouse who subsequently changes into a monster and back whenever he hiccups rather than Jekyll using the formula on himself and becoming Mr. Hyde.
• The Here Comes the Grump episode “Witch is Witch” had Terry and Princess Dawn encounter a friendly witch who would become an evil witch every time she said the word “nasty”, she would change back into her nice personality when she said “nice”.
• The Huckleberry Hound Show: Played for Laughs. In the episode "Picadilly Dilly", Huckleberry Hound is tasked with capturing the deranged criminal Picadilly Dilly, a pastiche of Mr. Hyde. The person behind the latter is Dr. Jikkle, who has become addicted to the serum that transforms him into Picadilly Dilly. Huckleberry, as laid back as he is, cannot recognize Picadilly even when the latter is running around him while giggling evilly.
• Several times in Jackie Chan Adventures is Jackie split into a good and bad side, usually via the Tiger talisman. These two sides are the same person and represent the balance in all humans of a good and bad side. Ironically, this occurs in one episode in which Jade is performing in a play about Jekyll and Hyde. It's not really "good" and "bad" though so much as "moral pacifist" and "amoral badass":
  Jade (pointing to amoral Jackie): You're evil! EVIL!
  Uncle: Not evil. Only misguided.
• The second Superhero Episode of Jimmy Two-Shoes, "The Terrific Trio", featured a large, green monster that constantly attacked Lucius out of spite. It was eventually revealed to be Samy, who was constantly transforming thanks to one of Heloise's potions that magnified a person's inner rage.
• Kaeloo: The eponymous character, who is normally a cute, gentle frog, transforms into a huge, buffed, sadistic toad whenever she gets angry. Some episodes imply that she knows what she's doing, but others imply that she has no control over this.
  Kaeloo: What did I do this time?
• There are some Looney Tunes cartoons exploiting this trope that Friz Freleng didn't direct:
  • "The Case of the Stuttering Pig", directed by Frank Tashlin: Mr. Goodwill, the lawyer, exploits this trope to get rid of a group of piglets so he can appropriate the house they just inherited from their Uncle Solomon — Goodwill is the next heir in line. He drinks two glasses of well-shaken Jekyll and Hyde juice to turn into a monster.
  • "The Impatient Patient", directed by Norman McCabe: Daffy Duck goes to Dr. Jerkyll's to get cured of his severe case of hiccup. The place is outright scary but the doctor turns out to be a complete scaredy-cat. So, to successfully frighten the duck and cure him, Jerkyll concocts and drinks a formula to transform into Mr. Hyde. Not that Hyde is any less of a doofus (here his name is Chloe, for whom Daffy had been searching to deliver a telegram).
  • "The Prize Pest", directed by Robert McKimson: Porky wins a prize in a radio contest. Cue Daffy Duck inside a gift box being delivered to his door. Naturally, Daffy starts causing mayhem in Porky's house, which gets him kicked out of the place. In response, Daffy lampshades this trope — in the lawn, he concludes that he'll have to "use his Jekyll and Hyde routine on this one". He then proceeds to exploit it by scaring Porky into submission. You see, if you mistreat Daffy, he turns into this hideous, fanged duck monster. But if you treat him nicely, he can be the loveliest of pets. In truth, Daffy merely messes the feathers on his head and puts some fake fangs on his beak.
• Mary Shelley's Frankenhole has the Jekyll and Hyde, whose serum causes John Belushi to turn into Jim Belushi. Victor also ridicules him for being his own monster.
• Monster Farm: One of the monster animals in is Dr. Woolly, a meek and bespectacled sheep who mutates into a deranged brute named Mr. Ewwe whenever he gets wet (getting wet again changes him back).
• Motor Mania: It features Goofy as the mild-mannered, friendly Mr. Walker. However, whenever Mr. Walker gets into his car, he becomes the ill-tempered, violent, and reckless Mr. Wheeler.
• The Perils of Penelope Pitstop: The Hooded Claw rented a house from Jekyll and Hyde as part of a plan to capture Penelope in "London Town Treachery", inviting Penelope and the Ant Hill Mob for tea while disguised as the Earl of Krumpet. After realizing there was no tea there, he improvised with some random ingredients. He planned to have the Bully Brothers capture Penelope while he distracted the Ant Hill Mob with the tea. However, the tea turned them into seven Mr. Hydes and they captured Penelope. To get their Sentient Vehicle Chugaboom to cooperate, they gave him some of the "tea" and he also became a Mr. Hyde.
• The Real Ghostbusters episode "The Two Faces of Slimer" had a leak in the Containment Unit unleash some ectoplasmic energy that infected Slimer and caused him to transform into a larger, uglier, and more vicious ghost (dubbed "Big Green" by the Ghostbusters) whenever he went to sleep.
• The Robonic Stooges: The episode "Dr. Jekyll and Hyde Curly" has Dr. Jerkyll creating his Red Hot Atomic Pepper while in prison. He dusts it all over himself and, as a result, an ugly, Mr. Hyde-like head grows in the back of his head. With the extra strength that the head provides, they both escape from jail and proceed to kidnap Curly. Jerkyll eventually captures all three stooges and dusts his Pepper over them as well, with the same results. The heads control their bodies (but not minds) to make them do Jerkyll's bidding. Every application of the Pepper has the Running Gag of the person not realizing they just got a head on their nape, with the head answering:
  That's what you think!
• Scooby-Doo, Where Are You!: "Nowhere To Hyde" (season 2, episode 1) mixes this with the standard "Scooby-Doo" Hoax. A diamond necklace is stolen by a figure people see is the Ghost of Hyde. The gang (after circumstances from confronting Hyde) follow him to a house in the woods where they meet Dr. Jekyll, who says he's the ghost of Hyde after attempting to mix and test a vitamin formula. The standard investigations and chases ensue and after Hyde is captured, it turns out the Hyde was Dr. Jekyll in a mask who tried to frame his housekeeper for the crime.
• Norman Osborn and the Goblin in Spider-Man: The Animated Series; unlike most depictions, this version of Osborn was a decent guy (or at least trying to be one), while the Goblin was as homicidal as ever.
• The Static Shock episode "Tantrum" had Virgil Hawkins/Static's classmate Thomas Kim transform into a purple behemoth whenever he got angry. Static even compares the transformation to Jekyll and Hyde.
• Tom and Jerry:
  • Dr. Jekyll and Mr. Mouse: Desperate to stop Jerry from drinking the milk he stole, Tom pours all sorts of poisons on the said milk. Instead of killing Jerry, it transforms him into an invulnerable super mouse with super strength. Unlike other cases of this trope, Jerry is aware of himself during his transformation and there's no trigger to set it off. That and the fact the one who creates the serum (aka Jekyll) is not the one suffering its effects.
  • The episode "See Dr. Jackal and Hide" of The Tom and Jerry Show, which is a reworking of Dr. Jekyll and Mr. Mouse. In this instance, it's a human scientist who tests a growth serum he created on himself. Predictably, everything goes wrong and he transforms into a long-haired, monster that chases Tom and Jerry until the effects wear off. He doesn't remember a thing and randomly switches back to Hyde mode.
• Transformers:
  • The Autobot Punch adopted a Decepticon personality as Counter-Punch, so as to play a double agent. He has lost some sense of self-identity because the Counter-Punch personality takes over, leaving him with a sense that he's missed out on the past hour or so.
  • It also happened in Beast Machines, with Savage and Noble. Savage is a blind, insane, vicious dragon, while Noble is an intelligent and cunning wolfbot. Subverted, in that they're Megatron, playing their sympathies to get into position.
• Morph from X-Men: The Animated Series, after coming Back from the Dead, often wavered back and forth between his normal, "Jekyll" self and a semi-undead "Mr. Hyde" alter-ego who blamed the X-Men for leaving him behind on a failed mission. It turned out he was mind-controlled by the season's Big Bad, but the effects didn't leave him for a good while afterward. At one point, he even hides out with a theater troop, where he performs "Jekyll and Hyde", using his shapeshifting powers to play both roles.
• Yogi's Space Race: Captain Good and Phantom Phink; actually a subversion, since "Captain Good" was a disguise to begin with.^note He only did "good deeds" in order to keep up the charade. Also parodied in one of the Space Race biography segments which describe Phantom Phink^note An original character created for this series. as Jekyll's descendant. With "Dr. Jekyll" looking like "Captain Good" and "Mr. Hyde" looking like "Phantom Phink".
• The Proud Family: In "Who You Callin' A Sissy?" it's revealed that Michael Collins has a monstrous Hyde persona that may have supernatural abilities.

Other

• TV Tropes: Sugar Wiki and Darth Wiki.
• Nasuverse: The Trope Namer shows up in Fate/Prototype: Fragments of Sky Silver as Berserker, and in Fate/Grand Order as an Assassin whose main mechanic is transforming into a Berserker. Although Henry Jekyll remains a Nice Guy Bishounen in both media, Edward Hyde is a wolfman-like monster in Fragments but remains fully human with wild hair and bloodshot eyes in Grand Order.

Real Life

• According to Colin Willson's History of Murder, the Thugee cult of India were sort of a Truth in Television example of this achieved through brainwashing, as they would lead normal lives most of the time, but then commit mass murder when seized by bloodlust. Wilson includes comments from Thugs to the effect that while generally they treated their killings as committed as within a dream, many felt that this murderous life was the real one rather than their respectable life.
• Musth, a hormonal surge experienced periodically by adult male elephants, can turn even the friendliest of pachyderms into a temperamental, violent threat.
• Locusts live as timid, solitary grasshoppers until their population gets too concentrated, at which point their hormonal levels shift and they begin swarming, migrating en masse and devouring every bit of vegetation in sight. And sometimes they're not even that fussy.
• The infamous Zodiac Killer claimed this in one of his letters. He said that he would "lose all control" to his Zodiac persona soon, and set up a bomb to blow up children. However, this may have been just a trick to humiliate the police once again.

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Jekyll Jekyll Hyde! Jekyll Hyde Hyde! Jekyll!
Jekyll Jekyll Hyde! Jekyll Hyyyyyyde!

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