The fate of Springfield Elementary rests on Bart and his test scores, and Homer finds way to make money with his own parking meter.

Bart gets in trouble on Grandparents Day at school and is forced to hang out with Skinner's mother as punishment. After spending time with various grandmas in the neighborhood, he learns the benefits of hanging out with the elderly, but eventually recognizes the dangers of taking advantage of them. Meanwhile, Peekimon Get has taken over the town of Springfield.

Homer discovers that Maggie is a whistling savant and launches her baby-celebrity career. Meanwhile, Marge impresses Fat Tony with her interior design taste, and he hires her to style his brothel.

As future Lisa writes her college application essay for Harvard, she recalls past disappointing birthdays that helped shape her.

When Bart goes missing, the town puts together a search party to find him. After most give up hope, Sideshow Bob manipulates Millhouse into revealing where Bart is hiding.

Mr. Burns will build a doomsday ark after he believes that the end of the world is near when he sees an old Orson Welles show about Nostradamus. Meanwhile, Professor Frink comes up with a new way of testing everyone in Springfield after Burns wants a test to determine who should go on a spaceship with him.