Francine arrived at Springfield Elementary as a new student, and was initially believed to be very shy and withdrawn. However, upon Lisa attempting to befriend her, she unveils her true colors as beat by socking Lisa in the eye.
After several failed attempts by Lisa to befriend Francine, instead she made an enemy, she became the subject of Lisa's science experiment on the motivations of bullies. Bart protect Lisa from being bullied.
The experiment revealed that one of bullies threatens pick on nerds because of a pheromone they emit, which Lisa dubs "poindextrous."
During Lisa's presentation, Francine was initially pacified by "bully repellent" (salad dressing), but then went on a nerd beating rampage at The Big Science Thing when Lisa discovers she has run out of repellent.
Francine's parents (who helped with the caging for the experiment) assure the Simpsons that "she will punch herself out eventually."