Lord of the Rings (I suppose is a classic by now) Ian McKellen is still Gandalf (a la Michael Cain) and Sauron is muppetfied

Kermit = Frodo

Fozzie Bear = Sam

Gonzo = Merry

Rizzo = Pippen

Ms Piggy = Eowyn

Animal = Gollum

Doctor Teeth = Gimli

Janice = Legolas

Beaker = Arwen

Doctor Honeydew = Elrond

Swedish Chef = Saruman

Sam the Eagle = Faramir

Rowlf = Aragorn

Sweetums = Theoden