Bewitched/WMG

Samantha had been married to two different men named Darrin.
Samantha divorced the first Darrin for being a lousy father who purposely stunted his daughter Tabitha's magical development. Samantha then married a second mortal whose name was Darrin, quickly, so her daughter would not have to go without a father figure; and she met him at the first Darrin's workplace, being too much of a busy homemaker to find a replacement elsewhere. Naturally, finding another guy in such a short time that it was seamless, this guy was as big a jerk as the first guy and also discerned Tabitha from developing and using her witchly powers. Samantha keeps marrying jerks because she's a nitwit who drank martinis when Tabitha was still in Sam's womb. Good thing Tabitha has her good loving grandmother.

Magic is symbolic of masturbation.
Samantha vows to stop as symbolized by her marrying of an uptight non-magic-using man. The couple usually keep their daughter Tabitha from using magic. Nonetheless, Sam and Tabitha use magic at times when alone. Sometimes magic seems taboo. Aging sometimes alters magical ability and control.

Every case of The Other Darrin on this show was actually The Nth Doctor
Aunt Clara screwed up one of her spells and turned Dick York into Dick Sargent. She ended up doing the same thing to Louise Tate, Mrs Kravitz, and Darrin's dad too. With some help from Endora, she altered everyone's memories as well as all pictures so that everyone(even Sam) think that's what they always looked like. Clara was going to undo all the damage later, but she accidentally turned herself into Esmerelda. This explains why Clara is neither seen nor mentioned in the later seasons.