The Joker has stolen a bomb that could threaten Gotham and reduce it to a crater. When Batman is informed, he feels the only way to find the Joker is to enlist the help of the Joker's nutty sidekick, Harley Quinn.
This was another great Harley episode, which provided some development for the character. She acts as delightfully looney as her puddin' in this episode, and the part where she sings about the Joker was really funny. We actually see her doubting the Joker and his wicked schemes, as Batman and Robin try to psyche her out, and she actually tries to kill Joker. But the end makes a statement about Joker and Harley's relationship: it's abusive and even when Harley starts to see the Joker for the twisted mind that he is, they always end up in each others arms again.
Mark Hammill was his usual twisted Joker self, making this episode such an enjoyable watch.