From Muppet Wiki

Mark Zeszotek was the Muppet Supervisor for Sesame Street between the years 1996-2000, although he was part of the Sesame Street team for years prior. He was awarded numerous Emmy Awards for his work on Sesame Street. Zeszotek passed away in 2004.

Zeszotek built and/or designed several characters including Grizzy, Sherry Netherland and others.

• The Adventures of Elmo in Grouchland (1999) (project supervisor) - built Grizzy
• Elmo Saves Christmas (1996) (V) (Jim Henson's Muppet Workshop)
• Sesame Street - Muppet Supervisor (1997-2001)
• The Muppet Christmas Carol - Muppet Supervisor
• Muppet Treasure Island