The Joker unleashes a lethal laughing gas in Gotham City that, when exposed long enough, will drive everyone to insanity.
- April Fools' Plot: The episode takes place on April Fools' Day, an early scene featuring Alfred "drawing Bruce a bath" (on a piece of paper). Bruce retaliates by the episode's end by pretending to take the priceless Ming vase he broke out of his salary.
- Cape Snag: A version of Batman's detachable clasp is shown when his cape becomes trapped in the grip of a robot Joker henchman — Batman quickly detaches his cape and spends the rest of the episode capeless.
- Disproportionate Retribution: Inverted, after Batman destroys the Joker's pet robot, Captain Clown (which Joker considers murder, since Captain Clown was his best friend). Joker retaliates by.... dumping a forklift full of smelly garbage right on top of Batman.
- Getting Crap Past the Radar: Captain Clown's Mecha-Mook status (see below) allows for him to be dispatched in a manner that'd be impossible to show with your standard flesh-and-blood henchman. It also allows Joker to avert the Never Say "Die" clause and chastise Batman for "killing" him.
- I Know Kung-Faux: One of Joker's goons tries to intimidate Batman with quasi-martial arts posing and yelling "Hi-ya!". Batman effortlessly puts him down in about 3 seconds.
- Large Ham: The Joker gets a few extra-hammy ones, "You KILLED Captain Clown!!!!" and "Your going to melt just like a grilled cheeeeeeeeeeeese sandwich!!!"
- Mecha-Mook: The "Captain Clown" robot piloting Joker's laughing-gas barge.
- Priceless Ming Vase: Alfred smashes a Ming (he had been driven mad by one of The Joker's poisons) and afterward felt ashamed, and was even prepared to accept being docked pay from Bruce Wayne as punishment.
- Punch! Punch! Punch! Uh Oh...: When Batman realizes that Captain Clown is really a robot.
- Shower Scene