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.
Principal Skinner: You're not supposed to be able to get outside our network.
Nelson: You shouldn't have made your password, "password".
Principal Skinner: It was the name of the street I grew up on, Password Drive.
I like to cry at the ocean, because only there do my tears seem small.</i> Nelson