Martin

Martin Prince is the second kid unlocked in the game, preceeding Milhouse Van Houten.

Simpsons Wiki Description
Martin Prince, Jr.  is  Bart 's classmate, and is  Lisa 's rival in intelligence. He is  Nelson Muntz 's favorite target for bullying, except for  Milhouse. He is an academically brilliant teacher's pet, and is portrayed as a stereotypical nerd. Martin is a 4th grade student at Springfield Elementary School. He is sometimes shown as Bart's friend due to the fact that he is occasionally seen with Bart, along with Nelson and Milhouse, though the fact remains that Bart still taunts him.