A middle-aged schoolteacher, John Martin, takes a sip from the fountain of youth and thereafter - and the least unexpected time - reverts to being a 12-year-old again. His wife and son learn of his predicament, and even try to cover things up by claiming that Little John is actually Big John's nephew. Of course, John would find himself converted at the most inconvenient moments, and all kind of shenanigans would happen as a result of trying to keep his odd condition a secret. Herb Edelman plays John Martin, Robbie Rist is his little self. The show was executive-produced by Sherwood Schwartz.