While The Joker has been awesome for about 75 years now, his crazy-lady sidekick Harley Quinn has only been awesome since the '90s. She first appeared in Batman: The Animated Series and was quite a hit, because really, the only thing fanboys would love more than The Joker was The Joker with boobs.
Warner Bros Television
They even gave her collar boobs just to be safe.
When Quinn first appeared on the show, she came complete with an over-the-top cartoony voice that was just this side of maddening. This was no coincidence. The voice, provided by actress Arleen Sorkin, was a pretty important part of Harley since Harley herself was inspired by Arleen Sorkin, and specifically this scene from the soap opera Days Of Our Lives.