Glenda Jackson - S5.E13

Glenda reveals herself to be Black Jackson the pirate captain, and she takes over the Muppet Theater with the help of Short John Silver (Sweetums) and Eric, a heartless pirate parrot (in disguise as a penguin). They tie Kermit up, turn the theater into a ship, and cast off to look for buried treasure. The show ends with a musical battle at sea, with Gonzo and a crew of chickens fighting to save Kermit and the theater.