Fatgirl is an annoying sidekick of Fatman, which is dumb seeing how she's not even the slightest bit as fat as him. She really needs to shut up, but she's good at beating up bad guys.
She lived most of her life with her uncle, Officer Weirdo. On "bring your freaky kid to work day", he brought her, and Fatman came to the station to warn about the danger of Bane of Losers. He tells how Fat Robin was almost killed by this monster of a man, and she agrees to be Fat Robin's temporary replacement. She makes out with Fatman, and after Fat Robin gets better, they are both his sidekicks, making his migraine get worse.
Powers and Abilities
Fatgirl has all sorts of powers that let her do lotsa stuff. She is on a special diet that grants her level two Super Fat. She can also pick locks by smashing her fat into a door until it breaks. She can also play the piano at a third grade level. Her fatness could confuse her enemies by making them think that she's pregnant so nobody kicks her and gets arrested for kicking her.