Just in time for Halloween, CBS aired the Star Trek episode Catspaw October 27, 1967. True to the mood of the season, this episode includes witches, a spooky castle, wizards and a gigantic black cat.
Sylvia and Korob are aliens who try to "connect" with humans via some sort of telepathy but only manage to tap into the subconscious where humans keep their superstitions and stuff of nightmares. Thus, they think this spooky mumbo-jumbo is normal.
The worst thing about Sylvia is her appalling sense of style. Talk about the stuff of nightmares.