I recently learned about Black Bart, a pseudo-spin-off sitcom based on Blazing Saddles and starring Louis Gossett, Jr. Only the pilot episode was ever aired. But — allegedly — an entire four seasons were filmed, and remain unreleased (possibly unedited and incomplete) to this day.
The story goes that Mel Brooks' lawyer had written a clause in the movie's distribution contract with Warner Brothers to prevent them from taking control of the Blazing Saddles IP — no sequels, spin-offs, et cetera — unless they did so within six months of the movie's release. This was meant to be an absurd stipulation; after all, it's hard to just make a TV show suddenly in six months. But Warner Brothers rose to the challenge, and rushed out sloppy production just to retain the rights.
Western spoof concerning the adventures of a black Sheriff and his fast-drawing sidekick fighting corruption and bigotry in the old west. Based on Blazing Saddles (1974). Many more episodes were filmed after this pilot but never aired because while the studio was contractually obligated to make them in order to keep the rights to Blazing Saddles, due to a contractual loophole they never had to actually show them.
This film was made due to a clause in Mel Brooks' contract for Blazing Saddles (1974), that forced the studio to make a television series adaptation within six months of the film's release to retain the rights. They did four seasons, at least, of a television series and were able to hold onto the rights.
The video above shares this tidbit, allegedly from Brooks himself (although the source isn't clear):
My lawyers, bless their souls, came to me and said, 'Warner Bros. is going to try and take away your control of the movie. Let's put in a crazy condition that says they can't do any sequels unless they make it right away or make a TV show out of it within six months.' Which is brilliant. They couldn't make a sequel in six months, and the movie was too vulgar to be a TV show. Now it would air in family hour if that was still a thing. So the lawyers put that in, never thinking they'd make a TV show. … In 1977, three years later, Warner Bros comes to me and says they want to make another Blazing Saddles, and I say, 'No. You don't have the right to do that.' They say, 'Yes we do, we've been making a TV series and still control the rights.' What TV series? I haven't seen a TV show. They take me onto the lot, into a projection booth, and show me three episodes.
You can find the pilot on the 30th anniversary Blazing Saddles DVD release.