The episode "Carpe Noctem". This includes a unique Mistaken for Gay, when the guy in Angel's body briefly believes Angel is gay; he hears a reference to Fred and assumes it's short for Frederik rather than Winifred.
Illyria taking over Fred Burkle's body to live again in season five.
The Avengers (1960s) in "Who's Who???" (subtitle: "Steed goes out of his mind. Emma is beside herself."). Steed and Emma's minds are switched with those of two enemy agents. They did not switch voices, if only because the plot demanded that the enemy use the heroes' hijacked bodies to infiltrate British security. In an amusing touch, after each commercial break, the episode also includes a "reminder" about the swap to the viewer, but the supposedly helpful voice-announcer merely gets progressively more confused.
Behind Her Eyes: This is Rob's evil MO. The first time, he convinces Adele to swap bodies with him but refuses to switch back. With Louise, he tricks her into leaving her body so he can occupy it.
In "The Witch", teenager Amy Madison's witch mother swaps bodies with her so that the mother can have a second shot at eternal fame and glory as a high school cheerleader.
Then in the fourth season, Faith gets a posthumous gift of Applied Phlebotinum from the Mayor that lets her pull this trick on Buffy.
A rare heroic version occurs when Willow is kidnapped by Amy and Warren. She possesses Buffy to lead her to where she is imprisoned.
And the Scoobies again possess Buffy, giving her all their powers in return, to help fight Adam.
Warren nearly succeeded in stealing Willow's body.
This is Eddie's endgame in luring Mike back to Iron Hill in Channel Zero.
One in particular is "Freaky Phoebe", in which an evil witch named Mara takes over Phoebe's body.
This is how the comics avoided having to pay for Shannon Doherty's likeness. Prue was able to rejoin the main cast and unite all four sisters by possessing a comatose witch whose appearance was very different.
Cleopatra 2525 has an episode, "In Your Boots", where recurring villian Creegan does this to Hel.
The Master has been known to do this from time to time:
In "The Keeper of Traken", the Master, at the end of the 13th and final regeneration of his Time Lord body, which is hideously decayed, plans to use the power of the Keeper to seal the body of the Doctor. Unfortunately for him, the Doctor escapes, forcing him to steal the body of Tremas, Nyssa's father. However, he considers this a temporary situation and spends much of the rest of the original series determined to extend his life, preferably through a new set of regenerations.
In the 1996 TV movie, he takes over yet another hapless human and attempts for a second time to steal the Doctor's body.
The Master takes this to the ultimate extreme in "The End of Time" part 1 by turning the entire human race into himself.
The spin-off audio "The Two Masters" sees the Master do this to himself; one of his older incarnations is manipulated by the Cult of the Heretic into attacking the burnt Master who was the last body in his original regeneration cycle so that the Cult can transfer the past Master into his future self (only telling the younger Master that the older Master is a dangerous renegade). The Cult's goal is to create a Reality-Breaking Paradox by killing the future Master in his past body, but the two Masters are able to escape and the Seventh Doctor eventually convinces them to return to their rightful bodies.
In "The Power of the Doctor", the third time's the charm for the Master, who uses stolen technology from Gallifrey to force the Doctor to regenerate into him, transferring his mind into the Doctor's body at the same time. Dressing in parts of outfits of previous Doctors, the Master plans to destroy the Earth and ruin the Doctor's reputation. However, thanks to Yaz, Vinder, and a hologram of the Doctor, the Master is forced back into the machinery and the process is reversed, restoring the Doctor and forcing the Master back into his own body.
Happens repeatedly in "New Earth", where Cassandra takes control of Rose's body to replace her old dying, immobile body.
Cassandra-in-Rose: Look at me! From class to brass! Although... [she pulls the zipper of her jacket down slightly and runs her hands over her body] Oh... curves... oh, baby... [she bounces up and down, Chip following suit] It's like living inside a bouncy castle!
She even spends some time hijacking The Doctor's body. Hilarity Ensues:
Cassandra-in-Doctor: Ah, ah! Two hearts! Oh baby, I'm beating out a samba!
When hijacking a plague victim: "Oh, sweet lord! I look disgusting!"
She finally winds up in the body of her abject worshiper, Chip, for her last few minutes of life.
"Utopia": Remember the ChameleonArch, the Gadget Watch that can serve as a Soul Jar for a Time Lord temporarily turned into another species, such as a human? And remember that opening the watch will turn the Time Lord back to normal? Well, unlike John Smith in the earlier story, Professor Yana doesn't get any warning of what will happen when he opens his pocket watch and The Master takes over.
Happens to the TARDIS in "The Doctor's Wife". As a slight twist, the body snatcher stuffs the original inhabitant into a specially prepared brain-drained slave, not its old form.
A story arc in the Doctor Who Magazine comic strip: A fish-like alien tries to replace the Eighth Doctor's human companion Izzy, looking to escape their past. The plan backfires, the bodysnatcher dies, and Izzy ends up stuck in the other body with apparently no way to return to normal. Several stories pass with Izzy struggling with her now-inhuman appearance, before the bodysnatcher turns out to be not so dead...
In the Twelfth Doctor novel The Crawling Terror, an insectoid alien general uses this technique to swap consciousnesses with Clara Oswald — and their bodies are on different planets at the time. The Doctor has to figure out how to reprogram the machine that facilitated this to reverse it.
Dollhouse: Seemed almost inevitable for a show about brainwashed, sexy, young humans you can rent and have temporarily reprogrammed to be anyone you want. Sure enough, by episode 10 ("Haunted"), it comes up (briefly) when a murder victim is put inside one such body to confront her killer. Then, three episodes later, in "Epitaph One," we learn that soon, Rossum, the gigantic corporation running the whole thing, will put the Dolls' bodies up for sale as biological "upgrades" — new bodies for the minds of aging clients, and of course, corporate executives. "Epitaph Two" makes it worse, as Rossum executive Matthew Harding seems to wear his bodies with rich food and then discards them, putting himself in a new, fit body.
In one episode of The Dresden Files, the Villain of the Week has this as his modus operandi. Usually when he switches bodies it kills the old one, but Harry has to figure out how to avert that when he takes over Murphy's body.
Harrison Wells was replaced by Eobard Thawne, who took on Wells's appearance.
Season 4's Big Bad Clifford DeVoe does this to Ralph Dibny, after Body Surfing through several other metahumans beforehand, as Dibny's body was the only one that could contain so many metahuman abilities without degrading. Fortunately, it turned out that he had to keep Ralph's consciousness intact in order to keep the body alive and Ralph was eventually able to regain control.
Done at least twice on Ghost Whisperer. The first time Melinda had to deal with both the possessor and the possessee's spirits; the second time was done by Melinda's recently deceased husband. To his credit, he made sure his new body's former owner had passed on first.
Hemlock Grove: When Olivia becomes terminally ill due to an anti-Upir virus, she plans on hijacking someone else's body with her downloaded personality. She first attempts it with a billionaire CEO, but the imprint becomes damaged due to their lack of genetic compatibility. She then successively tries to download herself into all three of her children.
Forcibly done to Sylar by Matt Parkman to contain Nathan's mind, on Heroes. Of course, this being Sylar, he quickly turns the tables by hiding out in Matt's mind and taking over his body and torments Matt's sanity in hopes that Parkman will be desperate and terrified enough to reunite Sylar's mind with his body. Matt, to his credit, attempts a Taking You with Me but it doesn't work and Sylar is reunited with his body anyway.
Midway through Kamen Rider Build, it's revealed that Soichi Isurugi has been possessed by Evolto, an alien Soichi encounters on Mars, the whole time. Later, Evolto switches to Ryuga (in order to get back his DNA from Ryuga and then Sento (in order to try and take advantage of his higher Hazard Level) before getting a body of his own.
On Lost, the Man in Black can do this after being turned into the smoke monster by assuming the form of those who have died. He most notably does it to Locke during the last two seasons.
Twice on Lost in Space: In 'Follow the Leader' John Robinson is possessed by the soul of a conqueror; Doctor Smith in 'The Space Creature', so the eponymous monster can get to Will Robinson.
One episode of series 3 of Misfits has the gang working at a hospital as part of their community service. While Kelly's in the room of a comatose patient, machines start beeping and as she's freaking out Kelly grabs the coma girl's hand, triggering her power to switch bodies with whoever touches her. The girl in question, Jen, spends the entire episode in Kelly's body as she tries to get back with her boyfriend while the main characters attempt to swap the two of them back.
October Faction: A dead warlock can be summoned into a living body, provided their ashes are on hand. This is Alice's plan—she has the ashes of every warlock Presidio murdered when they destroyed her home, and she summons them back on a mass scale. However, they are not all onboard with this, feeling that they have moved on and it's not fair to the people whose bodies they're inhabiting.
On Once Upon a Time, Peter Pan casts a spell that allows him to steal Henry's body in order for him to escape Neverland and to avoid being sucked into Pandora's Box.
In Quantum Leap Sam takes over somebody's body in the past and that person takes his body in the present. Usually, the person in the present simply waits or sleeps through the experience, but one person escaped the facility and caused some trouble with a Grand Theft Me of his own.
At least, that was how the concept of leaping started out. The "rules" grew rather murky in the show's final seasons, sometimes hinting that Sam was taking on a person's appearance rather than inhabiting his or her physical body. (In one episode, for example, Sam leaps into a double amputee...but is still able to walk.)
In the Red Dwarf episode "Bodyswap", Lister allows Rimmer to use his body for a week with the promise of Rimmer getting him into shape (in return, the Holographic Rimmer is able to touch, smell, and taste for the first time since his death). When Rimmer spends his time eating and sleeping (causing Lister to actually gain weight), Lister demands his body back — only to have Rimmer outright steal it the next time he falls asleep.
Tina Greer has posed as Lex, Chloe, Whitney, Lana, Clark, Jonathan and her own mother. Eva Greer (who may or may not be related) has taken the form of Chloe - even passably fooling Clark.
Clark and Lionel once switched bodies, while Lionel was in prison.
Isobel had possessed Lana in season four, and brought back her fellow witches who possessed Lois and Chloe.
Dawn Stiles had possessed Lana, Martha, Lois, Clark, Chloe, as well as a few extras.
Jor-El once possessed Lionel.
A random ghost possessed Chloe in pursue of revenge.
Bizarro has killed multiple hosts during his Body Surf, then impersonated Clark for several weeks after becoming his physical double. Lana has taken it hook, line and sinker but Chloe realized he is not the real Clark.
Zod once possessed Lex, and Faora once possessed Lois.
Brainiac once possessed Chloe, knowing that Clark would never hurt her.
"Holiday": There is a device that swaps Daniel's consciousness with that of a very old man (who had apparently built the device for that purpose, to prolong his own life), as well as the minds of O'Neill and Teal'c. Hilarity Ensues.
The Goa'uld are all about this, especially since body-switching keeps the symbiote alive for up to thousands of years. The Tok'ra are something of a subversion of this trope, since they never take unwilling hosts and they share the body. So are the Asgard, who survive by swapping bodies with mindless clones created for this purpose.
And done significantly more seriously in SG-1's ninth season, except it is Daniel and Vala who (accidentally) seize control of bodies in another galaxy, only to (accidentally) leave just before getting the people they swapped with killed by being burned at the stake.
Later in the season, Vala jumps into Daniel's body from the Ori galaxy to warn SG1 of the coming Ori invasion.
Done slightly more seriously in the Stargate Atlantis episode "The Long Goodbye", where the last survivors of two enemy factions possess the bodies of Weir and Sheppard so that they can play out the end of their war and one can "win", wreaking merry havoc across Atlantis in the process.
Teyla's partial Wraith DNA unfortunately leaves her open to possession when she tries to make mental contact with them in "The Gift". However, with a psychic boost from her unborn child, she is able to turn the tables and take over the body of a Wraith Queen in "Spoils of War".
Stargate Universe has the traveling stones, which allow for voluntary mind transfer. But on several occasions, once the swap occurs, the new occupant does things the original would never have condoned. When the original swaps back in, Hilarity Ensues.
In "Metamorphosis", the Companion takes over the body of the dying Nancy Hedford, preventing the death of her physical body and forming a symbiont.
"Return to Tomorrow" has the aliens of the week temporarily take over the bodies of Kirk, Spock and a female crewmember in order to build themselves new bodies. Unfortunately, the one in Spock's body has no intention of returning it.
In "The Passenger", a disaster on a prisoner transfer ship frees a criminal with personality-transference implants hidden in his fingers, leaving the crew to play Spot the Imposter for the rest of the episode.
Inverted in "Invasive Procedures". Verad doesn't put his personality in Jadzia's body; he puts Jadzia's personality (well, part of it — the Dax symbiont) into his body.
The Prophets did this to Sisko's biological mother, Sarah, in order to ensure his existence. Once the Prophet left, she ran off.
In "Warlord", though this time, the thief dies a few seconds before stealing Kes' body. That he is able to fool even Neelix for as long as he does is just a bit disturbing.
In "Vis á Vis", an alien criminal swaps bodies with Tom Paris, and later on, Kathryn Janeway.
Star Trek: Picard: Lore tried to usurp the Android M-5-10 golem in "Surrender" by absorbing Data's memories. But when he claimed all of Data's memories, Data re-asserted himself and absorbed Lore instead, turning it into a Fusion Dance.
There are numerous instances throughout the entire show of demonic possession, angelic possession, and shapeshifters stealing unfortunate victims' identities, to name but a few.
Demons are treated as mooks, and Sam and Dean often kill the host body while killing the demon. This is discussed onscreen a few times, but they never stop completely. There are also key moments over the series when a good character is revealed to be possessed by a demon such as John Winchester or Bobby Singer.
Angels must get their host's permission before possessing them, but this is often portrayed as problematic with religious people, such as Castiel's vessel Jimmy, saying yes without comprehending what it entails.
It's rare for ghosts to be able to possess people, but a few angry spirits are shown to have this ability.
In Season 2, Meg possesses Sam for an entire episode, going on a murder spree and terrorizing Jo.
In Season 4, Sam and Dean meet their half-brother Adam only to discover that it is, in fact, a ghoul who has taken Adam's form and their real brother has been Dead All Along.
In Season 9, there's a complex case wherein Dean tricks Sam into inviting the angel Ezekiel into his body so the angel can heal him but unbeknownst to Dean, it's not the good angel Ezekiel whom Cas has vouched for but a more morally ambiguous Gadreel. In order to help Sam break free, Crowley possesses him as well, making it two supernatural entities and one human soul in Sam's body.
In the episode "Swap Meat", the main plotline is that Sam is forced via magic to switch bodies with a seventeen-year-old boy.
It turns out that the villain's millennia-in-the-making plan is for Lucifer and Michael to commit Grand Theft Me on Sam and Dean respectively, and then duke it out for the fate of creation. Neither brother is okay with this.
Fearful about what Amara will do to the world, Castiel invites Lucifer into his vessel.
In "Let the Good Times Roll", Alternate Michael goes back on his deal with Dean to share the latter's body after they kill Lucifer, leaving Michael in full control of Dean's body.
Tokusou Sentai Dekaranger and its adaptation Power Rangers S.P.D. feature an episode where the Monster of the Week has this as an ability and inflicts it on Hoji/Sky, leaving him to be trapped in an intergalactic criminal's body as a prisoner while the actual criminal gets to infiltrate SPD. Fortunately, they manage to sort it out one way or another (via Out-of-Character Alert in Dekaranger and Pet Positive Identification in S.P.D.). The Dekaranger version also reveals that the criminal had repeatedly been doing this to escape capture and punishment so many times he can't even remember what his original body was like — and because his crimes were on the level where he was pre-approved for deletion, it's very likely that he'd created an entire body trail of victims executed for his crimes that SPD was completely unaware of, of which Hoji had gotten dangerously close to being the latest.
In the Tales from the Crypt episode "The Switch", a rich old man wanted a better body in order to attract a particular young woman. He gradually had all body parts surgically swapped with those of a young man — a process that also left him dirt poor, as the donor required huge amounts of compensation. In the end, this was all in vain. The woman was a gold digger and ran off with the now rich donor.
In "The Trade-Ins", an aging man decides to get a nice young body, but can't afford it for his wife, too (and the company isn't allowed to offer financing), then decides to give back the body and die a natural death with his aging wife. It isn't mentioned how the company that was selling him the brand-new body or where they got it from.
In "The Self-Improvement of Salvadore Ross", this is the young man's idea. He discovers he has the power to exchange traits with other people (an ill-defined ability, but hey...), so he finds a very rich old man and gets the multimillionaire to trade his fortune for renewed youth. Now old and rich, he proceeds to purchase youth a year at a time from a large number of young men at a thousand dollars a shot... eventually leaving him back at his original age, but with a lot of money.
The Twilight Zone (1985): In "Gramma", a young boy named Georgie has his body stolen by his monstrous bed-ridden witch-grandmother.
Twin Peaks had at least four different people intermittently possessed by at least three different entities - both good and evil - all of which entities did so to hide who they were and what they were doing.
As of the season 3 finale, Klaus now possesses Tyler, thanks to Bonnie.
As of Season 5, the Travelers make this into a way of life with their "Passenger spell", which allows them to merge with and control seemingly anyone. They do this to get around a curse that prevents them from being able to really settle down anywhere for good. The passengers control over the possessed body can be temporary or permanent, depending on the rituals performed, though a special knife can kill the passenger and restore the original self either way. Notable people possessed include Elena, Sheriff Forbes, and Tyler (again).
The two-part episode "Dreamland I" and "Dreamland II" has Mulder accidentally switching bodies with a Man in Black named Morris Fletcher (played by Michael McKean) due to some space-time anomaly caused by an experimental aircraft. Fletcher is having great fun with it while Mulder is miserable and desperately trying to get his body back.
Episode "King's Crown", from the anthology Show Metal Hurlant Chronicles, which is adapted from a story from Heavy Metal Comics: in a certain land, a tournament is held every so often to choose the strongest man to be the new king. Entrants must be vital and free of diseases. Every winner becomes a cruel tyrant, but the hero of the story (called weak and frail all his life) wants to become ruler and end the reign of evil. He wins, and at his "coronation", he's bound, his skull is cut open by robot surgeons (after he wakes up), his brain is crudely removed over his screaming protests, and the brain of the previous king is transplanted from his freshly-dead, used up, obese corpse. The TV Show is adapted from the comics to the letter except for the very last scene: In the comics, the stress of the surgery sets off a congenital heart defect the hero suffers from, killing his body and the tyrant is slain. In the TV adaptation, however, the hero is perfectly healthy and the brain transplant is successful, the evil king is reborn in the hero’s strong muscular body and will use it to continue his reign of evil.
