While on a trip to Florida, John Martin stumbles upon the legendary fountain of youth and sips a handful of the liquid. The consequences are unforeseeable, for he begins to revert to his childhood at certain times that are neither predictable nor controllable.

Big John is cast as Captain Hook in his school's production of Peter Pan, while Little John ends up having to play Peter Pan at the same time.

John tries a new formula in the laboratory that he hopes will cure him from his conversions.

John Martin is detained when a sheriff demands his ID and he cannot produce it. He gets his freedom when his personality changes in prison.

John has summoned Mr. Boswell, Stanley’s dad, to account for his son’s continuous tardiness to class for five days.

Everyone braces for flu shots in the midst of a flu epidemic.

John believes he has discovered the secret of the Fountain of Youth, so he calls a press conference to announce his discovery.

Big John's voice in Little John's body and vice versa puts not only Martin in a squeeze but his family as well.

Stanley is again late for the class. The teacher is speaking to his students about the importance of facing up bullies. This leads to trouble for Little John when he's threatened by the class bully, Gasey.

John is assigned to find who is behind the vandalism inflicted on the school walls.

Little John receives a severe reprimand for having played unwillingly a joke on the school principal.

The school prepares for their annual Thanksgiving dance, "Plymouth Rock".

Homer wants to quit school and become a magician after believing he made Little John change into Big John.