Recursive Adaptation: The late 90s/early 2000s Sabrina animated series (and its versions of the cast, etc.) was adapted back into the comics, in the context of being flashback stories to Sabrina's junior high years.
Still another from Cheers: Diane is a lovely-yet-wicked witch whose cottage is on top of a giant beanstalk. And she's brunette—perhaps in an inside-joke Light Feminine Dark Feminine contrast to Diane, or...something.
Salem is Norbert Beaver in a cat's body. Seriously. The latter two telefilms (Sabrina Goes to Paris and Sabrina Down Under) starred Tara Strong as Sabrina's overseas friend.
The Other Darrin: Similarly to M*A*S*H, very few actors carried over from the original Pilot Movie to the series proper. Other than Melissa Joan Hart, only Michelle Beaudoin, who played Marni in the movie and Sabrina's (first) best friend, Jenny, in the series, appeared in both of them. Hilda, Zelda, Harvey, and the voice of Salem were all re-cast. Libby does not appear in the pilot; a character named Katie fills a similar role. There's also a character named Seth in the movie who acts as Wrong Guy First; he has no analogue in the series, as Sabrina is hot for Harvey (which is more or less requited) from the outset.
A more conventional example, during the show's run: the two actors who played Sabrina's father not only looked totally different but the replacement was visibly years older.
Cousin Marigold is another example, first played by Robin Ricker and later Hallie Todd.
Real-Life Relative: Recurring character Amanda (Sabrina's evil cousin) was played by Melissa's little sister, Emily Hart. Who, as noted above, ended up playing Sabrina herself in the cartoon.