Kermit the Frog is Jim Henson's most famous Muppet creation, first introduced in 1955. He is the protagonist of many Muppet projects, most notably on The Muppet Show, and Sesame Street, as well as in movies, specials, and public service announcements throughout the years. Henson originally performed Kermit until his death on May 16, 1990.

source: wikipedia