Nelson Muntz is the bully on The Simpsons and is voiced by Nancy Cartwright.  Nelson is probably best known for his class "Hah Hah" laugh he does at everyone.

Though Nelson is typically foun bullying Bart and other students, we've also seen his softer side as Lisa's boyfriend and even as Bart's friend.

Nelson Muntz Quotes

Bart: Boys and girls, Mrs. Krabappel, I come before you today to solve a riddle that has plagued mankind for centuries: What has four legs and ticks?
Milhouse: A walking clock?
Nelson: A walking clock!
Martin: I'd wager he has some variety of walking clock in that box!
Edna: Bart, is it a walking clock?
Bart: What?.....No, it's my dog.

Goon #2: Nelson, you're bleeding.
Nelson: Nah, happens all the time. Somebody else's blood splatters on me. (Sniffs) Hey, wait a minute. You're right. (to Bart) You made me bleed my own blood!

The Simpsons Quotes

Marge: Tomorrow night, it might be nice to go out for dinner.
Homer: Tomorrow night? Friday? Pork chop night? Marge! We haven't missed pork chop night since the great pig scare in '87!

Wow, now I see why they call you Miss Hoover. You must have been vacuuming for an hour.

Bart