Beulah is a witch and a relative of Sabrina Spellman. She is an aunt of Hilda Spellman and Zelda Spellman, possibly a sister of their mother.
Beulah lives in the Other Realm and always invites all of her relatives to her annual Halloween party, but her nieces Hilda and Zelda always reject the invitation on the belief that the party will be boring, rejecting the invitation for over 500 years. When they finally ran out of excuses, they reluctantly attend the party and discover the truth about Aunt Beulah, becoming trapped in the mental asylum that she lives in with their crazy relatives. However, Beulah reveals that it was all a party theme and that she's really not (that) crazy. Later when Sabrina told her that the Doll she sent as a gift has been terrorizing her and her friends, she assumed brought the wrong doll and travel with her to the Mortal realm to fixed her mistake. However upon seeing the doll, Beulah confirm that the doll was the right one but Zelda pointed out that in the Mortal Realm, Doll aren't evil. So to stop her Beulah sang in a opera voice, making the doll stop and promise not to do it again.
Aunt Beulah was played by Jo Anne Worley of "Laugh In" fame.