High Quality Content by WIKIPEDIA articles! Nelson Muntz is a fictional character from the animated TV series The Simpsons. He is voiced by Nancy Cartwright. Nelson was introduced in Season 1`s "Bart the General" as a bully but later turned into a friend of Bart Simpson. He is best identified by his signature laugh ("HA-Haw!"), his torn waistcoat, baggy shorts, bucked teeth and brown shoulder-length hair.