Percy Carey was one of the Kids on Sesame Street, who appeared in Season 7. In episode 0806, Big Bird found Percy riding on Mr. Snuffleupagus' back. NPR claims he appeared from age 5 to around age 9, and describes him as the first child to ride on Snuffy.
As an adult, he became an underground hip-hop emcee from New York City who goes by the names GM Grimm and MF Grimm. DC Comics' Vertigo comic label released an autobiographical graphic novel of Grimm's life in September 2007, Sentences: The Life of M.F. Grimm, which includes his time on Sesame Street.