Trying to find the title for a black and white horror film with stage props coming to life [closed]

I'm trying to find the title of this movie from my childhood.

Only scene I remember is that there is a theater and people are enjoying their show, which oddly enough features a big sized cardboard octopus that seems to run on automation gears on stage, that depict a scene from the sea like a storm or something. Kind of like how those shooting gallery duck moves on a flat screen in some fun fair.

I remember that the waves were moving like that. Somehow, the octopus came to life, and with its tentacles, started to drag a few of the victims from the audience seat, and when they were dragged on stage, the victims themselves became cardboard cutouts of the scene.

People start to panic and run for their lives but more horrific things happen as more people get dragged on stage. The story is trying to depict that when things get dragged on stage they became cardboard cutouts in the scene.

I think this is somewhere between 1920s till 1930s

It is most definitely from the U.S. I don't have any idea about actors - just the short plot that I remembered, as this was during the CRT era for television. I could barely make out the actor's faces, at all.