The Simpson family is out at the Singing Sirloin, celebrating Bart's First "A." When asked how he did it, Bart tells them it was studying (he witnessed seeing Principal Skinner and Mrs. Krabappel making out during head lice inspection, and he studied to get his mind off topic). Homer and Marge are proud of their son's achievement, until the waiter comes back saying Homer's credit card was just declined. Homer throws a bunch of other cards in his face and uses this as a distraction while the family runs for the door without paying. They fail to escape and end up having to work off their bill as the night's entertainment. When the Singing Sirloin closes for the night, they are allowed to leave. It is apparent that money is tight for the Simpson family as many cutbacks had to be made. Marge suggests to Homer that they talk to a financial planner.
The next day, their planner sees that Homer and Marge now have several mortgages, credit card debt and no savings. Their future continues to look bleak and at their current rate, they'd continue losing money even after they're dead. Higher intelligence reports tell their planner that Homer is just too stupid to stick to a budget, so she tells them bluntly: they need more money.
At the plant, Smithers is capable of requesting off work so he can work on his play about Malibu Stacy. Mr. Burns tells him he'll be capable of entertaining himself. In the cafeteria, Homer is drinking some beers to hopefully work up the confidence to ask Mr. Burns for a raise. Once the opportunity comes, he strikes the question, but Mr. Burns wants a laugh. After Homer struggles to come up with a joke, Mr. Burns hands him a glass of vanilla pudding and tells him to throw it at Lenny. Homer initially refuses, but reconsiders after Mr. Burns offers to pay him for it. Mr. Burns likes this new routine so much that he agrees to make Homer his "prank monkey."
As time goes on, Mr. Burns' pranks continue ranging from innocent enough (buying an expensive comic book and eating it in front of Comic Book Guy) to increasingly degrading (acting as a giant baby in the men's bathroom).
Later on, Mr. Burns' newest prank involves some time at the zoo. It's simple enough; Homer is to wear a giant panda costume, dance around and fall over, letting the zoo attendants see the zoo's panda is nothing but a fat, bald man in a panda suit. Lisa, who was in the crowd, starts to think that something is wrong. Suddenly, Homer is approached by the zoo's male panda, who seems interested in the new panda. Homer calls for Mr. Burns' aid, but Mr. Burns is busy laughing at this ruse. Homer, knowing he is on his own, tries to run, but trips and falls over a rock. The zookeeper thinks this is a miracle; they thought making the pandas breed would take years. The panda grabs Homer and drags him behind a curtain. Later on, Homer is able to escape from the sleeping panda and Lisa finds him.
As Lisa hears the whole story, Mr. Burns shows up and offers to double Homer's pay for that extra length. It is now clear to Homer that in this job, Mr. Burns only cares about his own personal enjoyment and much less about Homer's well-being. After Homer tells Mr. Burns off, he contemplates what to do with the dirty money he received. Lisa suggests that he be charitable with it. Homer donates the money to Costington's, where Mr. Costington is impressed by Homer's generosity and thinks he'd make a great Santa Claus.
At the parade, Homer is enjoying his charade as Santa Claus, but then Mr. Burns shows up asking Homer to perform one final prank. Homer refuses; he won't do it for any amount of money. He is tempted when Mr. Burns prices the prank at $1,000,000.
Later, Marge and the kids see Santa is dumping fish guts onto the crowd. Lisa thinks Homer just sold his soul, but is proven wrong when Homer shows up. But who is in the Santa suit? Mr. Burns is doing his dirty work himself. Homer tells us Lisa gave him an early Christmas present: the gift of dignity... and then the family is splattered in the fish guts.