After seeing a UFO Buster has a hard time convincing his friends of what he saw, and when he gets pictures of the flying saucer, Brain comes up with an explanation for each one.
After Buster defeats the Brain in a math contest, the Brain declares Buster the new brain and decides to become a comedian, until his friends convince him that he is still as smart as ever.
Unhappy about how much homework they have to do, Arthur and his friends dare each other to skip school, but their plans go wrong, leaving Francine to suffer the consequences.
Arthur's Grandma Thora, a marbles champion, trains him for the first-ever Elwood City Marbles Tournament, but does not tell him that she will compete against him.
