Cosmo Allegretti was born on April 6, 1927 in Manhattan, New York, USA as Cosmo Francis Allegretti. He was an actor, known for Prince of the City (1981), Author! Author! (1982) and Sorcerer (1977). He was married to Carol Lawrence and Ilolya Korody. He died on July 26, 2013 in Phoenix, Arizona.

Cosmo Allegretti created and performed several of the show`s best-known puppet characters, including Mr. Bunny Rabbit, who always tricked the Captain into giving him carrots, and Mr. Moose, whose riddles and knock-knock jokes invariably ended with hundreds of ping-pong balls cascading from above and hitting the Captain on the head. Allegretti was the actor who portrayed the Dennis the Apprentice, Miss Frog (the telephone operator), Mr. Whispers, Dancing Bear, Grandfather Clock, and Uncle Ralph characters. He was also the artist behind the Magic Drawing Board.