Elmo is a red Muppet from the popular PBS children's television show, Sesame Street. He made his official debut on the show in 1985, and has been a regular on the show since 1986 (his popularity increased starting in the early 1990s, and is now one of the most popular characters on the show today).
He was once sent to Ronald Reagan Reeducation Center for going to the wrong fundraiser, where he hanged himself.
On The Simpsons, Elmo is usually voiced by Nancy Cartwright. But on Sesame Street, he was originally puppeteered by Kevin Clash, who resigned in 2012 due to a scandal. He is currently puppeteered by Ryan Dillon.
In Bart-Mangled Banner while escaping Homer recounts that Elmo hung himself in his cell. But this is mostly untrue since he reappeared in four more episodes and the movie.