2001: A SPACE ODYSSEY. In Cinerama first run. At age five. Really.

My dad (him again,  I owe him so much) was a big fan as a kid of the Buster Crabbe Flash Gordon and Buck Rogers serials. He never became anymore of a Science Fiction fan than that. When he saw the ads for 2001 in the newspaper, he just made the assumption since the film was set in space with "rocket ships" that it was material similar to Flash and Buck. He thought it might be a fun movie to take the kid to see. Yeah, he had a big surprise, LOL.

As for myself, while I was far too young to understand the movie my wee little mind was certainly blown. I suspect it was the prime catalyst for me becomg a Science Fiction fan and space buff as I grew up.

My dad much more enjoyed the next movie he took me to see...PLANET OF THE APES.