^Thanks, now I know where to dig further.
I can accept weird things in a Batman story. The first episode of B:TAS had a man transforming into a giant bat, and I said "OK, why not?". But at least that was explained in passing in the same episode. Killer Croc, too - what is he? A crocodile-human hybrid, or a guy with a skin condition? Either way, I can accept it. I'm not sure Killer Croc was ever explained in any of the DCAU episodes.
I guess I was just surprised at the inclusion of an anthropomorphic toad in a story about a masked villian (typical of a Batman story) trying to capture or kill billionaires in Gotham City. Without the toad, it looked like a story that could be set in Nolan's Batman universe.