The Tingler (1959)

This was a hilarious movie. It is so silly, but Vincent Price is amazing as usual. This is from Wikipedia explaining the film's prologue: 

Much in the manner of Universal's groundbreaking Frankenstein (1931), William Castle opened the film with an on-screen warning to the audience:

"I am William Castle, the director of the motion picture you are about to see. I feel obligated to warn you that some of the sensations—some of the physical reactions which the actors on the screen will feel—will also be experienced, for the first time in motion picture history, by certain members of this audience. I say 'certain members' because some people are more sensitive to these mysterious electronic impulses than others. These unfortunate, sensitive people will at times feel a strange, tingling sensation; other people will feel it less strongly. But don't be alarmed—you can protect yourself. At any time you are conscious of a tingling sensation, you may obtain immediate relief by screaming. Don't be embarrassed about opening your mouth and letting rip with all you've got, because the person in the seat right next to you will probably be screaming too. And remember—a scream at the right time may save your life."

I think it would have been fun to see this in the theater when it came out. My favorite part of the movie was in the theater scenes where the lights go out and Vincent breaks the 4th wall in a sense.