Oh, sorry - the Muppets are...I guess you'd call them a puppet troupe? They're really big in my world, with tons of movies and a TV show and stuff. And they're really good, the puppets and the actors/puppeteers who work them are amazing.
Anyway, most of the theater here is humans playing humans, but when you get down in the arts scene, you can find some different stuff. There's WEPT, and there's the Shadowboxers (they don't perform as often, but they do shadow puppetry), and some of the cats down at The Canteen have an improv group (where obviously all the roles are done by cats, not humans).