According to Muppet Wiki, "Cookie Monster is one of the main characters on Sesame Street and
has been since 1969. He is covered with blue fur and possesses a pair of googly eyes. He loves to eat cookies,
but he can consume anything and everything, while making loud munching noises, usually like 'OMMMMMMM-nom-nom-nom-nom...'
He has a deep, growly voice and speaks with in a simplistic way (e.g., 'Me want cookie!'). He was originally the
'Wheel-Stealer' monster for the unaired 'Wheels, Flutes and Crowns' snack food commercial and an IBM training film called,
'The Coffee Break Machine' in 1967, and 'Arnold' for three 'Munchos' commercials in 1969. He then moved to Sesame Street
as an anonymous monster during Season 1 (1969-70). Until in Season 2 (1970-71), his name was implied, due to his obsession
of cookies. His most famous song is 'C is for Cookie.' He also hosts 'Monsterpiece Theater' segments as 'Alistar
Cookie.' During Season 33 (2002), he hosted 'The Letter of the Day' segments. Then, during Season 36 (2005), he learned
to eat a balanced diet and limit cookies as a 'sometimes food'."
Frank Oz (1969-present)
David Rudman (2001-present)
Jim Henson (The Ed Sullivan Show and commercials)
Joe Raposo (1969, in "Everyone Likes Ice Cream" - voice)
Caroll Spinney (1969, in "Monsters Whisper the Letter C" sketch)