Teaser: In another entry of the Secret Case Files of Batman, Batman and Robin fight Firefly in an adaptation of "The Rainbow Batman".
Main Plot: Joker gains Bat-Mite's powers, and he has his way with Batman. Meanwhile, Bat-Mite develops a crush on Harley Quinn.
- Adaptation Deviation: In the original Rainbow Batman story, Batman kept wearing a different colored costumes to distract people from Robin (Dick Grayson had made the news when he broke his wrist saving a girl, and Batman didn't want people to notice Robin had a broken wrist as well, which could expose his secret identity). Here, the Dynamic Duo is fighting Firefly using multi colored lasers with diferrent effects. The lasers don't effect objects of the same color, so Batman kept switching colors to be immune to the effects (the Rainbow Suit is the final upgrade to counter Firefly).
- Adaptation Distillation: The cut down the plot of Emperor Joker to the bare essentials of Joker getting the power of a 5th dimensional imp, killing Batman a bunch of times, and him being defeated via Talking the Monster to Death.
- Adaptational Protagonist: Batman replaces Superman as the protagonist for the story.
- Adapted Out: Pretty much every other character from the comic including Superman, Steel, Bizarro, Lois Lane, Lex Luthor, Mr Mxyzptlk, the Spectre, and the JLA are cut with only Batman, Joker, and Harley Quinn retained.
- Armor-Piercing Response: When Batman shows Joker a world without the Dark Knight is rampant with crime.Joker: My kind of town.
Batman: But you have no one to match wits with, no symbol of goodness to corrupt. Without Batman, there can be no Joker, no loose screws, no lost marbles, no bats in your belfry. In this world, you're perfectly sane. - Batman Gambit: After several deaths and resurrections, Batman says he can endure such torture, but he begs for his sanity to be left intact. Joker likes the prospect of driving his foe insane and enters Batman's mind, which is exactly what Bats was hoping for. His disciplined mind is more than a match for Emperor Joker, and he forces him to experience his greatest fear: a world without Batman. Crime rages out of control, but Joker can't enjoy it because a world without Batman means a world where the Joker is perfectly sane and no one of consequence. Batman will only free Joker from this personal nightmare, if he surrenders Bat-Mite's powers.
- Big "NO!": Joker's response to being shown just how utterly normal and sane he'd be without Batman.
- Break Them by Talking: Batman gets Joker to surrender by telling him without Batman, he's nothing.
- Composite Character: Bat-Mite takes over Mr. Mxyzptlk's role.
- Cute Mute: Harley when her voice is taken away by the Joker.
- Dumbass Has a Point: Harley argues against Joker entering Batman's mind, saying it could backfire. Already frustrated with her questions and comments, Joker responds by taking away her voice. However, she ends up being exactly right.
- Evil Counterpart: Miffed over Batman having a little fanboy, Joker creates one in the form of Joker-Mite.
- Eye Scream: When Batman was fighting Ted Eye Man he was able to stop him by tossing him a cactus resulting in him catching it with his ten eyes.
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Genius Bonus: One of the Joker's goons looks like Harold Lloyd, and has an iron right hand. The real life Lloyd lost a couple of fingers on his right hand early in his career when he was goofing around with a Cartoon Bomb that he assumed was a prop but had real explosives in it. For the rest of his life he wore a special prosthetic glove to disguise the missing thumb and fingers. - Lampshaded the Obscure Reference: Bat-Mite explains the origin of Ten-Eyed Man, noting how the show is really good at featuring figures from the Rogues Gallery that mainstream audiences just aren't very familiar with.
- Lighter and Softer: Let's just say the original source comic was a lot darker than the episode. In particular, Batman's many deaths were not Played for Laughs.
- Mythology Gag:
- When turned into Joker's court jester, Bat-Mite is dressed like the Batman: The Animated Series version of Harley.
- The design for Joker-Mite takes cues from when Jack Nicholson played the Joker.
- Nice Job Breaking It, Hero: With Batman having trouble during the fight, Bat-Mite had intended to help by transferring his powers to him. Joker got hit by the beam instead, causing everything to spiral out of control.
- Nightmare of Normality: After entering Batman's mind, Joker is forced to experience a world without the Dark Knight, where he is just a sane nobody. The Joker is so horrified by this that he agrees to surrender Bat-Mite's powers rather than spend another second like this.
- Oh, Crap!: Joker-Mite over the prospect of being the playmate of the re-powered Bat-Mite.
- Secret Identity Apathy: To Harley's surprise, Joker has absolutely no interest in unmasking the captured Batman. To do that to his "primal enemy" would make things far less fun.
- Shout-Out:
- The gang have a Silent Movie motif, with the men as Charlie Chaplin, Harold Lloyd, Buster Keaton, and Roscoe "Fatty" Arbuckle. When she's later rendered a Cute Mute, Harley "speaks" in the form of title cards.
- Batmite is reading an issue of the old DC "Who's Who" comics from the '80s while he explains to the audience about Ten-Eyed Man.
- Sociopathic Hero: While talking about Batman comics, Bat-Mite notes how Jason Todd's fate was decided by readers calling a hotline.Bat-Mite: [darkly] Guess how I voted.
- Spared by the Adaptation: In the original Emperor Joker comic the Joker uses his powers to turn Harley Quinn into a constellation in the sky so she can see the world go mad. Here Joker at most makes Harley a mute for back talking.
- The Starscream: Once Joker enters Batman's mind, Joker-Mite suggests to the other mooks that they ensure he doesn't come back by offing Batman now. Bat-Mite and Harley have to fight them off to keep Batman safe.
- Talking with Signs: Harley is eventually made mute with Joker's powers, and can only speak with old timey speech cards. She later weaponizes them.
- Villain Song: "Where's The Fun In That?"
- You Don't Look Like You: As part of the Silent Movie Shout-Out, Harley dresses like a flapper rather than a jester.
