One-shot villain Deadpan was voiced by Bebe Neuwirth, known for playing the very deadpan Lilith Sterin on Cheers & Frasier.
Throw It In: See that Moment Of Awesome from the first episode? Originally Freakazoid was just supposed to say "No!", but Paul Rugg improvised the rant.
According to the DVD commentary, it apparently went on for over 10 minutes, becoming increasingly disjointed and profane; they cut it off right before the cursing started.
What Could Have Been: The original idea was for the series to be a fairly straightforward superhero show with comedic overtones (basically, The Joker as a good guy) with Bruce Timm in charge. Spielberg, however, asked for a full-blown comedy. Timm bowed out, as he honestly thought he wouldn't do a full-blown comedy concept justice. This is perhaps a textbook example of Executive Meddlingimproving a show. (The New Batman Adventures episode "Beware The Creeper" is a glimpse of how Timm and Dini would have done Freakazoid!)
The series always skewed towards an older audience and there was serious consideration towards just putting it in prime-time (as was done with Pinky and the Brain). This is part of the reason why the second season largely had half-hour episodes instead of Three Shorts.