I often chuckle at the observation that Tim Curry and Michael Caine's respective roles in the Muppet films were so beloved because Michael Caine acted like all the muppets were real actors, and Tim Curry acted like he was a muppet. He would have an impressive range of serious / comedic roles anyway, but I admire the ability for an actor that successful to be able to put himself be in such a silly role that well too.