If Samantha can turn back time to correct a situation, why doesn't she do it more often when in a tough jam? Making Samantha this powerful for one episode is a plotting error that makes other plots less believable. Only a few episodes ago, Samantha can only do small things with her magic.
Humans cannot perform or learn witchcraft. That's frequently mentioned, particularly in "The Joker is a Card". However, in this episode, Samantha casts a spell such that the house, and all that is in it, cooperates with Darrin and his wishes. This way he is able to do magic without destroying the consistency.
(Darrin just sent down a paper flier and got a pencil, flying by magic, back)
Samantha: Darrin, before you get angry. Please be fair. You sailed something down to me, right? It was only fair, that I sail a little something back up to you.
Darrin: (argues) What I did was not only extremely clever and humorous, it was aerodynamically sound. What you did, was witchcraft.
(Samantha just made it possible that all the items in the house cooperate with Darrin, she encourages him to give it a try)
Darrin : (with a strong voice) Banana... come! ...Darrin.
Samantha: You don't have to sound like Tarzan.
Darrin: Well I never talked to a banana before.
This episode was filmed on November 18, 1964.
A Is For Aardvark very possibly refers to the first entry in the old grade school readers used to teach students the alphabet.