He is a character in the cartoon created by screenwriter and cartoonist Matthew Abraham "Matt" Groening called The Simpsons, whose full name is Bartholomew Jojo Simpson ( in Spanish "Bartolomeo Jay Simpson Bouvier"). He is the eldest son of the family, who despite the several decades that the series remained on screen is still about 10 years old. Bart would be an apocope of his first name, although he is actually a metathesis of English/brat ("brat, brat, spoiled", which fits more to his personality.
