Paul Dini, a writer and story editor on Batman: The Animated Series and Tiny Toon Adventures, co-created the original pitch for Freakazoid! with Bruce Timm. Although Timm had little involvement once the show went in a more comedy-oriented direction, Dini contributed several scripts throughout the first season. He also provided Expendable Lad's grunts.
Dini continues to be involved in Warner Bros. Animation's DC Comics projects. Perhaps his biggest claim to fame is that he created the Batman villain Harley Quinn, who has gone on to feature prominently in DC comic books, video games and feature films.