James “Jimbo” Jones, Sr., also known as Jamesbo, Dr. J, and Hector Gutierrez, is one of the bullies at Springfield Elementary, with Dolph Starbeam, Kearney Zzyzwicz, Nelson Muntz, and the Weasels. He is a 6th grader. Jimbo is the second-in-command of the bullies, being the leader when Nelson isn’t around, although Nelson has no interest in hierarchic systems. Jimbo is the tallest bully, and strongest after Nelson.

He constantly bullies Bart Simpson and other smaller children at Springfield Elementary. Jimbo wears a purple knit cap (originally no knit cap), a black short-sleeved T-shirt, emblazoned with a menacing skull (originally, a yellow short-sleeved dress shirt), blue jeans, and black and white shoes. Bart describes him as a good looking rebel who plays by his own rules. A real low-life, Jimbo is acknowledged as the leader of the bully gang in absence of Nelson. Jimbo is often seen hanging out with Dolph, Kearney, and sometimes Nelson. He is considered an outlaw or a “bad boy”. Despite his reputation as a bully, it is sometimes hinted that Jimbo is in fact Christian, with strong moral standards. At one point, when he reveals to Martin that the “paint” vendor that he got the unicorn tattoo from was actually a tattoo parlor at the Skewed Over event, he notably showed hesitance at beating up Martin at that point as he “had it rough already”, even stating to the other bullies that it might not be a good idea to beat him up, although he ultimately decides to beat him up with the other bullies. He has been kicked out of all 4 Space Mutant movies. According to the episode “Beware My Cheating Bart”, he has a bald spot underneath his hat (although he didn’t have it earlier in Bart of Darkness or Lisa the Drama Queen).