Movies that shouldn't have sequels, but do.
part 3: some Cult Classics.
HENRY: PORTRAIT OF A SERIAL KILLER
spawned one sequel; HENRY 2: MASK OF SANITY
THE HILLS HAVE EYES
spawned 1 official sequel; THE HILLS HAVE EYES PART II
and finally; THE ROCKY HORROR PICTURE SHOW
spawned 1 sequel: SHOCK TREATMENT