How about Muppet walkaround characters? They could be in costume and wander around the Backlot area of DCA? I would love to get my picture taken with a life sized Bean Bunny, Fozzie Bear (Ahhhhhhh....wakawaka), and even Sweetums!
I was really disappointed after Muppets 3D that I couldn't get my picture taken with the "walkaround" Sweetums. I don't think I'd necessarily like to see Muppets characters roaming around the park, but I think it was a missed opportunity in the area near the movie itself.