At the Ace Chemical Plant, news reporter Jack Ryder is anchoring a live TV special on the career of the Joker, starting with his encounter with Batman at the plant that ended with his life-changing tumble into a vat of chemicals.
Joker, watching from above, decides to stage his own tribute to that fateful day, entering the scene, dosing Ryder and his crew with his trademark laughing gas, and then "re-enacting" his confrontation with Batman by tipping Ryder into another large vat of chemicals. Batman, having glimpsed Joker on the television, is quick to arrive at the plant with Robin. While Joker's henchmen keep them busy, Joker occupies himself with pushing the hapless Ryder back into the chemical soup every time he tries to climb out. For his finale, Joker gives Ryder an exploding cigar causing the chemicals to explode. Joker then fights Robin, knocking him into the plant's controls causing the tank to flush into the nearby sewer, forcing Batman to try and save Ryder while Joker escapes.
Ryder's burning coat is seen dissolving into the chemicals and he is presumed dead. However, Ryder survived and had a bizarre reaction to the combination of Joker gas and the chemicals: He transformed into an extraordinarily strong and agile maniac with yellow skin, green hair, and a rictus grin. Ryder runs around town for a while and decides that he should get revenge on the Joker. Ducking into a thrift store, he assembles a bizarre costume, preparing for a new career as a crime-fighter. Ryder uses his own credit card, alerting Alfred to the transaction. Alfred then alerts Batman to Ryder's antics.
Joker returns to his hideout, upset that someone is stealing his image. However, he finds that his henchmen are gone, Harley has given them the night off so she can throw a special, private party for Joker's "birthday" (that is, the seven-year anniversary of the incident that transformed him into the Joker). Harley rises out of a giant pie and offers to play, but Joker predictably tosses Harley out on her rear, telling her to "find the plagiarist who's been stealing my act!"
Ryder finds the Joker's thugs at the Stacked Deck and demands Joker's whereabouts, dubbing himself (based on one of Mo's remarks), "The Creeper!" The three thugs attack Ryder but he has no trouble taking them down. Harley starts moping outside the club when Ryder catches sight of her. Feeling an intense attraction, he accosts her, demanding to know where Joker is... and also her phone number.
Harley runs from the club with the Creeper in hot pursuit. She tries to kill him by dropping a heavy crate onto him, but the Creeper is unharmed. Pursuing Harley back to Joker's hideout, the Creeper confronts the Joker, who throws a vial of explosives at him. However, the Creeper is still unharmed and is only momentarily defeated when Harley hits him with her hammer into a stack of giant blocks. The explosion leads Batman and Robin there, where they begin their pursuit of Joker and Harley. The Creeper wakes up and pursues Joker and Harley as well. However, while driving the Jokermobile, the Creeper accidentally unleashes missiles behind him. The Creeper finally catches up to the Joker. Although the Creeper's mania is benign, his methods are so extremely wild and frantic that even the Joker begs to be arrested, clutching Batman's cape and crying, "He's a lunatic!" Batman cuffs Joker and injects the Creeper with a sedative.
Back at Ryder's apartment, Batman applies an antidote skin patch that returns Ryder to his normal state. Before leaving him to rest, Batman warns him that the patch must be left on to counteract the chemicals and assures him that his career isn't entirely lost. After they leave, Ryder examines the skin patch curiously, finding it hard to believe that a "little piece of cotton" can make such a big difference. Outside his apartment, there is a small sound of tearing fabric, and soon the Creeper's demented laughter is pealing from the window.
- In the documentary, it shows that the Joker worked for the Valestra mob, as seen in Batman: Mask of the Phantasm.
- The beginning of Jack Ryder's special on the Joker states that his former identity was unknown and that he operated under a variety of aliases. In two previous instances before the revamp — "Dreams in Darkness" and "Joker's Wild" — Joker was given the supposed "real name" of Jack Napier, the same name he was given for the 1989 Tim Burton movie. This episode makes it clear that Jack Napier isn't his real name and was merely an alias that Joker used at one time. This means that his true identity is left a mystery, like his comic-book version.
- According to the special, Joker's accident was seven years before this episode.
- Jack Ryder apparently enjoyed his alter ego as the Creeper, and would go on to join the revamped Justice League in Justice League Unlimited.
- The ejector chair of the Joker's car used by the Creeper for catching Joker and Harley was previously used by the Joker for escaping from Batman in "Joker's Millions".
Home video releases
- When Batman sedates the Creeper in the end, the syringe tube on the injector fully disappears into the device's narrow point, despite being made out of glass or solid plastic.
- On the Season 1 DVD of Freakazoid!, Bruce Timm mentioned his original ideas for the eponymous character were closer to the Creeper (and specifically, how the DCAU's Creeper turned out) than the over-the-top roads eventually taken, which caused Timm's departure from that show.
- The thrift store is called Ditko's Vintage Clothing, after comic creator Steve Ditko, and a mannequin resembling The Question is seen in the background. Ditko created both the Question and the Creeper.
- The title of this episode comes from the Creeper's original solo series from the 1960s, Beware the Creeper.
- The dramatized Batman in Ryder's documentary look similar to Batman in his very first appearance in Detecive Comics #27.
- Joker's gang in this episode—Mo, Lar and Cur—very closely resemble Moe Howard, Larry Fine, and Jerry "Curly" Howard—The Three Stooges. The Three Stooges were used as the inspiration for previous goons, but only vaguely.
- Joker's conversion with Harley Quinn is a nod to Tweety's line in "Looney Tunes".
- When The Creeper startles the woman in her apartment, he leaves, saying "Okay I love you, bye bye". This is a line frequently used by Mindy in the television series "Animaniacs".
- Harley Quinn's anniversary song to Joker is an homage to Marilyn Monroe's famous rendition of "Happy Birthday" to President Kennedy.
- During the episode, Joker accuses the Creeper of "stealing his act". Jeff Bennett, the voice of Creeper, went on to voice the Joker on Batman: The Brave And The Bold.
- Harley and Joker's escape float is similar to Disneyland/Disney World's "It's a small world" attraction—cute robot dolls from different cultures with a giant globe on top.
- Last appearances of Robin and Alfred Pennyworth in The New Batman Adventures.
Creeper: I'd better slow down, try to figure out logically what's going on here...
Creeper: Breaking news! And if you break it, you have to pay for it. And now the weather: Partly ga-ga with a fifty percent chance of schizophrenia.
Creeper: I want to strike terror into the hearts of criminals!
Creeper: Last time we met, you were working for—dramatic pause—the Joker!
Creeper: "The Creep". Oh wait, too negative. I HAVE IT! I am, drumroll, please... I said, "DRUMROLL, PLEASE!". (starts beating Lar's head)
Harley: What do you want?
Batman: Who are you?
Joker: He's a lunatic!
Harley: He's the creep who's stealing your act!