The House That Dripped Blood (1971)
Ironically, just as Peter Cushing (Moff Tarkin) played 'Dr. Who,' in those classic films, he stars with one of the actual Doctors in this anthology flick.
Basically the tale revolves around a house which deal with 1) a mystery writer who encounters a mad strangler, who appears as a form of his own creation; 2)Two men obsess with a familiar woman in wax; 3) A child who (for some reason) dabbles in witchcraft.. but it's the fourth tale which deserves some major riffing..
In this one, Jon Pertwee (Third Doctor), plays an overbearing actor who is working on a horror film, and is sent to a shop to fetch a cape. Regrettably, the cape (surprise, surprise) is cursed and ends up transforming Jon into a vampire.
This was one of the Hammer anthology films which was supposed to be horrifying but comes off being hilarious since these tales are somehow tied to the house in general. But never really tell what happened to the residents afterwards as it goes from one tale to the next (the ones which inexplicably survive).
Definitely a classic made for riffing...