Joker takes over the mantle of Batman, running around Gotham beating up and gassing people for any offense he sees, regardless of the severity of the crime or whether it's even a crime in the first place. Soon proving that he's the superior Batman, he decides there's nowhere left for Bruce to go but to become the new Joker (pulse optional), injecting him with a slow-acting but lethal form of Joker Venom that soon has him acting like his arch-nemesis.
This episode provides examples of:
- Actually Pretty Funny:
- Alfred dubiously remarks that one of Bruce's Sanity Slippage puns is a "good one, sir."
- Batman, usually so serious, surprises Joker with a joke that actually makes him laugh.Batman: A man walked into a bar, and said… "Ow."
- All Crimes Are Equal: When pretending to be Batman, Joker's punishment to anyone committing a crime, no matter how minor, is to use his deadly Joker Venom on them.
- Bait-and-Switch: In the beginning of the episode, it looks like Batman is chasing a man for jaywalking, but then the real Batman arrives to help the man. We then get another look the fake Batman revealing him to be the Joker impersonating his arch-nemesis.
- Berserk Button: Penguin drops all civility and attacks when Bat-Joker calls him "Gotham's second biggest criminal."
- "Blackmail" Is Such an Ugly Word: Joker uses his venom on the mayor's wife (for using an express lane at a store with one item over) and then demands a "fee" for his "services". It's very unsubtle.
- Cassandra Truth: Batman warns Penguin not to open the can with the pop-out Joker venom snake. Penguin thinks that if Batman wants the can, it must be something he wants too since both Joker and Batman messed with his theft.
- Clark Kenting: Joker's "secret identity" just has him dressed as an office worker.
- Disproportionate Retribution: How Joker deals with "crime" when posing as Batman. He gassed the mayor's wife just because she had eleven grocery items when in a ten items or less checkout line.
- Dramatic Drop: A villainous example; Joker drops the pop-out toy snake that contained the Joker Venom upon seeing that Batman had swiped the piece containing the venom itself in time to add it to the antidote he had made earlier, curing himself.
- Even Evil Has Standards: Penguin is annoyed that Joker is messing with his crime, since it goes against Villainous Valor, and then freaked out when a laughing Batman shows up and makes a quip.Penguin: …Okay, now you two are starting to creep me out.
- "Everybody Laughs" Ending: The episode ends with Joker and Penguin laughing uproariously at Batman's joke. Penguin briefly pauses in confusion as to why he's laughing, but as he's been dosed with Joker venom, he quickly resumes laughing. Batman, meanwhile, is just standing there silently.
- Felony Misdemeanor:Reporter: Joker has inexplicably turned to fighting crime. The crazed catch? It seems the offenses he targets barely qualify as crimes at all.
- Forgot Flanders Could Do That: Joker's fighting ability was toned down after "The Bat and the Belfry" due to fan backlash, but here it's back in full force. Kind of hard to be the Batman if you're not a good fighter.
- Honor Before Reason: Penguin apparently refuses to interfere with Joker's "gas all of Gotham" schemes out of "professional courtesy," despite the fact that he'll die if one of those schemes ever does work.
- I Have Your Wife: The Joker victimises Mayor Grange’s wife, in response to the latter taking too many items to a checkout.
- Insane Troll Logic: Apparently, Joker considers hopscotch and graffiti to be the exact same things. (Justified in that he is insane.)
- Innocently Insensitive: Joker’s venom begins to affect Bruce a little too much while he’s visiting Mayor Grange’s wife in the hospital… with her husband.
- Irritation Is the Sincerest Form of Flattery: Subverted. The Joker imitates Batman to purposely annoy him. (And it works.)
- Kill and Replace: Sort of the Joker's goal, although it's doubtful anyone would mistake him for the real deal.
- Knight Templar: Joker as Batman.
- Locked Out of the Loop: Penguin hasn't learned from the news about Joker becoming a Knight Templar Batman.
- Never Say "Die":Bruce: ...enforcing the body into increasing bouts of laughter until...
Alfred: Joker said he wanted an arch-enemy, but he didn't say a pulse would be required. - Oh, Crap!: The Joker when he realizes Batman took out the venom from the pop-up snake and gives himself the antidote. He drops the snake and doesn't put up a fight when Batman knocks him into a bar.
- Only in It for the Money: Aside from his primary goal to annoy Batman with his new persona, Joker is only fighting crime to get paid by the city ("Crimefighting ain't charity work") and if the Mayor refuses to pay the bill, then Joker will make Gotham pay dearly.
- Pursued Protagonist: "The Laughing Bat" begins with a man running through the streets from someone in a Batman costume while pleading that all he did was jaywalk, only to be gassed into a paralytic state. It turns out his pursuer is Joker, who has decided to screw with Batman by dressing up like him and victimizing misdemeanor offenders.
- Sanity Slippage: Bruce under the effects of the Joker's toxin starts to make tasteless jokes and laugh uncontrollably.
- That Man Is Dead:Batman: Costume party's over, Joker.
Joker: Joker? Didn't you hear? The Clown Prince of Crime’s checked out. - There Can Be Only One: The fight between Batman and Joker-Batman.Batman: Gotham has one Batman too many.
Joker: Which means one of us has gotta go.
Batman: My thoughts exactly. - Tomboy and Girly Girl: The two girls that Joker almost pummeled.
- Villainous Valor: Referenced; Penguin says that it's common courtesy for two criminals to not intentionally disrupt each other’s schemes.
- Visual Pun: A pop-up snake in a can is the method of administering the lethal Joker Venom.
- "Where? Where?": This exchange.Mayor Grange: Joker!
Joker: (looking round in panic) Where?! - Would Hurt a Child: Joker was going after two girls playing hopscotch (for marking up the sidewalk with chalk) before Batman made his move.
