I maintain that Muppet Casablanca is a solid winner.
Kermit and Piggy as Rick and Ilse, obviously. Gonzo as Lazslo, Fozzie as Louis, Rolf as Sam. The cafe scenes are basically Muppet scenes already - tell me you can't imagine the "Vot Votch" couple as Muppets.
Operation Eric Furry
In the better timeline, we've had another muppets remake of a classic movie every five years or so, and they're all classics.
People fight over which is best: Muppet Count of Monte Cristo, with Kermit as Edmond Dantes and Eddie Redmayne as Albert, or Muppet Moby Dick, with Ian McShane as Ahab.