It is vaccination day at the school and John turns into a kid and he gets vaccinated. Then at the end of the episode, he becomes a man and the other teachers take him to get vaccinated again, much to his chagrin.

John believes he has discovered the secret of the Fountain of Youth, so he calls a press conference to announce his discovery — but his "discovery" shows no signs of panning out as he had believed.

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