Here are two scenes from 1953's "The 5,000 Fingers of Dr. T".
It is best known for being the only feature film ever written by Theodor Seuss Geisel ("Dr. Seuss"), who was responsible for the story, screenplay, and lyrics.
The plot revolves around young Bart Collins, who lives with his widowed mother Heloise. The major blight on Bart's existence is the hated piano lessons he is forced to endure under the tutelage of the autocratic Dr. Terwilliker. Bart feels that his mother has fallen under Terwilliker's sinister influence, and gripes to visiting plumber August Zabladowski, without much result. While grimly hammering away at his lessons, Bart dozes off and enters a fantastical musical dream, in much the same fashion as The Wizard of Oz.
In the dream, Bart is trapped at the surreal Terwilliker Institute, where the piano teacher is now a madman dictator who has locked up all non-piano-playing musicians in a dungeon and constructed a piano so large that it requires Bart and 499 other enslaved boys (the aforementioned 5,000 fingers) in order to play it.
I think that in 1953, movie audiences simply weren't ready for anything even close to this.
Jaw dropping isn't it? I have to wonder how audiences reacted to that in 1953. My guess is that it was something like the scene in "The Producers" after the "Springtime for Hitler" number.
And then there is the memorable ride in the Dungeon Elevator: