I would have liked to have seen at least one of the female superheroes from the show, but I think if it were clobber girl then it would have caused the issue of a stretch dude skin not being released (the two characters go together, IMO), as Bart just had the Bartman skin released. They could have added Lucy Lawless, though, without it being an issue because of the Collector (in the episode she reminds the kids that she is not Xena, but Lucy Lawless). But then they would have to go through the process of getting the rights to use her image in the game, I believe... Which is probably way more of a hassle for them.
Too bad, though. All of them would have fit in to the event very nicely! :D