Homer embraces the "old person lifestyle" when Grampa and two other octogenarians move into the Simpson home, while Nelson becomes friends with Bart, who defends Nelson's love for hand-me-down underwear.
Bart stumbles upon the local mafia boss, and starts working for him on the side. When Principal Skinner goes missing after punishing Bart, he and Fat Tony's gang are suspected of killing him, but they try to get Bart to take the rap.
The Simpson family receives a severed monkey's paw which can grant wishes, Bart gains magical powers which he uses to turn Homer into a Jack-in-the-box, and Mr. Burns uses Homer's brain to create a robot.
The results of a standardized test steer Bart in the direction of law and order at Springfield Elementary School. However, Lisa becomes so depressed by her results that she turns to juvenile delinquency.
The Simpsons wind up regretting paying for an expensive surgery for Santa's Little Helper. He then runs away from home, winds up in the animal shelter, and is adopted by Mr. Burns to become an attack dog.
Milhouse falls in love with Samantha, a new transfer student, and Bart becomes jealous of all the time they are spending together. Homer orders a subliminal weight loss tape, but is given a vocabulary builder by mistake.