In this episode, contrary to an often-used theme from other episodes, it was possible for Samantha to undo Endora's spell without any additional explanation. Sam was able to turn little Darrin back to normal Darrin and also the other way around.
Samantha: (to little Darrin) After all, what do they expect from a 10-year-old kid? (Darrin's not pleased) Sorry darling, I was only trying to make you feel better.
Little Darrin: Sam, nobody likes a smart-aleck witch.
Samantha: (scolds Endora) Mother, it isn't funny. How would you feel, if you woke up one morning and found yourself twenty years younger?
Endora: (very pleased with this image) No comment.
Darrin: (angry about Endora) She could have stunted me out of ten years growth. As a matter of fact, she did.
Samantha: Twenty actually, but who is counting?