Hoppy, the new pet that Barney and Betty got for Bamm Bamm, causes major havoc and nearly ends Barney's friendship with Fred.

Fred reverts to childhood after getting hit on the head with a bowling ball. After looking for a doctor, Barney finds a mad scientist that uses electric shock to swap personalities.

Fred begins inventing again and creates a reducing formula called "Fred-O-Cal" to take off weight. This formula winds up shrinking Fred to less than a foot tall.