RHPS, which came out in 1975, had a spectacular ending where the mansion turns into a ship and flies off into space. This morning on the Roku channel B-Movie TV I was watching a French horror/farce film called Tender Dracula(1974), and in the final scene the mansion/castle turns into a ship and rockets up and out of sight.
Coincidence, or homage?
I doubt it was intentional, for a couple of reasons.
The original stage version premiered in 1973, the year before Tender Dracula was released. The script has a line about “beaming” the castle back to the home planet. I have no idea how this was staged in the original production, but the concept of the castle leaving Earth was already in the story.
IMDB says Tender Dracula was released in August 1974. RHPS (the film) was already in production at that point.
It’s possible that somebody involved with RHPS saw the French film and got the idea to have the castle launch like a rocket, but I think it’s probably a coincidence given the limited timeframe.
It didn’t occur to me to check the RHPS script until after the edit window closed. The script says “We see the entire castle surrounded by a giant beam of light and then vanish into space”—nothing about it physically launching upward, so that idea evidently came up later in the process.
I still doubt that they got the idea from Tender Dracula, though. My impression is that the French film wasn’t particularly popular or successful. But it’s possible.
About twenty years ago, I saw a theatrical production of the Rocky Horror Show. If I recall correctly, it was a community theatre production, so it likely didn’t have a lot of money for special effects.
Anyway, at the end, when the castle is supposed to take off, the three survivors were grouped stage right, while lighting effects occurred offstage left. The sound effects were of a rocket launch (likely taken from a recording of an actual NASA launch), and the survivors’ heads rose in unison, as if they were watching a rocket rise up from the ground, offstage left. The whole thing may have been done on a shoestring, but was surprisingly effective to indicate that the castle was launching upwards.
I don’t know about “beaming” the castle, or how it was done in the original stage production, but most of the audience at the show I attended was sufficiently familiar with the movie, that the castle launching like a rocket was likely expected.
It’s a cool coincidence, but I think it’s just that.
Shit. Now I gotta go find and watch a crappy old Frenh film. Thanks, OP. 
Not related, but this thread brought to mind the deleted scene and song from the movie:
I just viewed TENDER DRACULA on youtube and it’s hard not to see a similarity between the rocket castle ending of both movies.
That said, go watch CARRY ON SCREAMING (1966-UK) with Rocky Horror in mind. Too many similar ideas to not think that Rocky Horror must have cribbed from it.