Bartholomew "Bart" Simpson is voiced by Nancy Cartwright (that's right, a woman!) and is Homer and Marge's only son on The Simpsons. Bart is an underachiever and was definitely much more of a bad boy in th ebeginning seasons of the show.
Now, Bart, although he has not aged, has certainly matured as a character. Do the Bartman people.
Bart: Hey, Mom. Did you save Dad's love letters?
Marge: Of course I saved them. Well actually, there's only one. It's more of a love postcard from some brewery he visited.
Homer: Maybe it's the beer talking, Marge. But you've got a butt that won't quit. They've got these big chewy pretzels here (undecipherable slurring) five dollars?! Get outta here!
Bart: Wow, the side of Dad I've never seen.
Bart and Lisa: (Singing dull) Hot dogs, Armour Hot Dogs.
Grampa: Sing it like you mean it!
(Grampa plays harmonica and the kids sing it with style.)
Bart and Lisa: What kind of kids eat Armour Hot Dogs?
Bart: Fat kids.
Lisa: Skinny kids.
Bart: Kids who climb on rocks.
Lisa: Tough kids.
Bart: Sissy kids.
Milhouse: (Sticks head from the window.) Even kids with chicken pox love--
Family: Hot dogs, Armour Hot Dogs.
(Grampa stops playing harmonica.) The dogs kids love to bite!
Lisa: Doesn't this family know any songs that aren't commercials?
(Everyone except Lisa starts singing the "Chicken Tonight" jingle.)