Bartholomew Jojo "Bart" Simpson is the delinquent son of Homer and Marge Simpson, the director of the adult sector of NintenD'oh, a known murderer, the secret identity of Bartman, Cupcake Kid, Cupcake Lord and El Barto, worshipper of the Krusty the Clown, champion skateboarder, and arguably the most dangerous child in the world, although still called a hero.
Bart was born a long time ago, and appears to be immortal like the rest of the Simpsons. Once he hit ten years old, he stayed that way forever, despite celebrating his eleventh Christmas and Birthday SO MANY TIMES! Bart is also a very powerful person, being able to defeat even Magikarp in hand to hand combat. He is also in possession of several bombs, so yeah, don't mess with this kid.