I think I'm going with Kelsey Olson. Miss Piggy can't complain about that, as she is a model. But she has good range of expressions for a model, so...
It's not actually a Muppets game, it's pan-fandom. It's set in a mental asylum e.g. I already play the 10th Doctor from Dr Who, and he thinks he's an alien. Miss Piggy I have down for histrionic personality disorder, amongst other things :-) Game is here if you're interested: ccrpg