Ronald Duck

From Muppet Wiki

Ronald Duck is a friend of Mickey Moose's who hangs around backstage in episode 220 of The Muppet Show. Though he speaks in an erudite voice, Ronald is a parody of Donald Duck, from the soundalike name to the sailor suit outfit.

The puppet used for Ronald was first seen in episode 113 as the duck played by Cynthia Adler in the Veterinarian's Hospital sketch.