At the end of The Adventures of Buckaroo Banzai they promised to return in Buckaroo Banzai Against the World Crime League. It never happened. BB was a cult movie, but at first it was a pretty poorly followed one, and I don’t think it ever achieved the status of The Rocky Horror Picture Show (which didn’t promise a sequel, but did deliver one).
At the end of The Sword and the Sorcerer they promised to bring back the hero, Talon, in Tales of the Ancient Empire (Which empire? Don’t ask) It never happened. Supposedly the film made more money than any other independent film for 1983 (there are no gods), so the producers just took the money and ran. Hawk the Slayer evidently promised a sequel at the end (I still haven’t seen it).
The James Bond movie The Spy Who Loved Me promised that the next Bond feature would be For Your Eyes Only. Apparently the folks at Eon, eyeing the profits being raked in by Star Wars, decided they wanted to jump on that bandwagon, so they pushed in Moonraker as the next entry. (Like TSwLM, written by the puerile Christopher Wood, who would go on to give us Remo William: The Adventure Begins. Probably just as well they didn’t do FYEO next. It turned out to be was the best Bond film in many years. Can you imagine what it would’ve been like if Wood had written it?)
We probably won’t see sequels for either League of Extraordinary Gentlemen or Ven Helsing, even though the endings of both films seemed to point in that direction. Yeah I know the reason why (they sucked)…
Free Enterprise promises the sequel “William Shatner vs. The World Crime League” (spoofing BB of course). Wikipedia says there’s a sequel in pre-production but there’s no source for it and IMDB has nothing.
Clerks: “Jay and Silent Bob will return in Dogma” Mallrats: “Jay and Silent Bob will return in Chasing Amy” Chasing Amy: “Jay and Silent Bob will return in Dogma (we promise)” Dogma: “Jay and Silent Bob will return in Clerks 2: Hardly Clerkin’” Jay and Silent Bob Strike Back: “Jay and Silent Bob have left the building.” Clerks II: “Jay and Silent Bob may return. As for now, they’re taking it easy.”
How about, “We’re making a sequel and you’re not in it”, which happened to Robert Wuhl, who played the reporter Knox in the 1989 Batman movie. Shortly afterward I saw Wuhl on some talk show and he was asked about the sequel and he said, “You mean ‘Batman 2: The Annuity’ ?” I think that wisecrack may have did him in.
The song “Jews in Space” became the song “Men in Tights.”
Although not promised as such- The sequel to Masters of the Universe (the Heman/Skeletor toy franchise movie) became Cyborg with Jean Claude Van Damme.