A: He is the voice of Homer Simpson!
... and Barney Gumble and Mayor Quimby and Grandpa Simpson and Groundskeeper Willie and Krusty the Clown and Hans Moleman and the Rih Texan and several others. He is Dan Castellaneta, a short, skinny, bald Italian. He also played a recent live part as Will Smith's stock-brokerage instructor in "The Secret of Happyness."
Click:
http://www.imdb.com/name/nm0144657/