When I was about 7 years old I used to believe that when I was watching on TV, the scene when Kong was climbing up the Empire State building in the 1933 movie "King Kong", that if I was in New York City I would actually see the giant ape climbing up the building.

I saw The Wizard of Oz on TV while very young and thought the Cowardly Lion was always talking about his "cabbage". The lack of logic didn't bother me, since I couldn't follow the plot anyway and was just watching for more flying monkeys and dancing midgets
After seeing Mary Poppins, I immediately went home, grabbed an umbrella and began practicing to fly with my umbrella by jumping off the couch and holding my umbrella. I would measure how far I jumped each time and actually believed I would eventually fly.
I had watched the movie signs. I thought an alien would pop out of my closet.I was nine now i am 11.
I still do!!
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It was my first time going out to a see movie . (Back when Disney's Pinnochio was "in") For some reason, I thought there were ghosts inside the theatre
I used to think, when I saw pictures Alfred Hitchcock, that he was Freud. I have no idea how I knew who Freud was or where I saw pictures of Alfred Hitchcock at age 7, but there you have it!
i used to love to play with my barbies and dolls. well one day i watched "chuckie" with my mom. i was so scared of my barbies after that, that my mom had to move them into her room.
when i was little i used to share a room with my sister. she had a poster from the movie "the crow" and i was terrified of it. i was always afraid that when i turned the lights out he would come out of the poster and try to kill me. i rarely slept with the lights off....
When I was young, I believed that the special effects in movies were real. I couldn't understand why movies had such cool things like robotics, etc. But for some reason we weren't allowed to have things like that in everyday life. (Arm got cut off? No problem! We can rebuild it. We have the technology!) :)
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I used to believe that movies were all true (occuring) stories. For years I went around calling Sylvester Stalone Rocky.
I use to think that everytime I watched a video there were little people in the video tapes preforming or doing something to make the movie run. And when I watched Waynes World about once a day, I was working them to hard.
While watching Bambi with my mom for the first time, I became confused as to what happened to his mother. I asked my mom where she went and was told that she had gone shopping with her friends. I never thought it at all odd for a deer to go shopping, despite my better judgement, since of course my mother would never lie to me...
I not only believed this, but I also believed that at the end when Bambi's wife has two fawns, it was his mother having more children. She was the only doe I knew of in the movie, after all, and she was still living.
When I was very young I had a conversation about the origin of gremlins with my grandfather after seeing the Gremlins film. He told me that in WWII the army and air force reported that gremlins destroyed their equipment and somehow were affiliated with the japanese. A few weeks later, now convinced that gremlins truly existed I was sitting in the bench area of a local mall. An old man gave me a few pennies to through into a water fountain and make a wish. I told him he can keep his change, 'I only throw gremlins in fountains' (after the mildly traumatic climax of the film).
When I was 8, I watched Superman I and fell in deep love with the Christopher Reeves version. I was convinced that he was watching me through my window at night because he lived on Mars (it was red and HE wore red) and was someday going to knock on our door (with flowers) and say, "Is Crystal Home?" in this really longing romantic voice. I wore my favorite pajamas every night in anticipation of his arrival.
When seeing films from the advent of motion pictures, I assumed that everybody used to walk differently than we do now, and that's why people's movements were so jerky. It was years later I learned it was the difference in the film equipment used.
When i was little i used to think that actors actualy had to grow into the parts that they played , for instance if the movie started of with a character as a little girl they had to wait for her to grow up so they could film those scenes , i have no idea where that came from, cause really nothing backs that up ! but the whole concept of other actors and makeup just wasn't gettin through.... but its ok after my mum nearly wet herself laughing she set me straight !!!!
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I use to believe that if you rewind a tape or a movie you were making the actors do it over and over again.
I had a friend who, as a child, used to think that name of our local movie theater was "a theater near you" because of the commercials that always said "coming soon to a theater near you" :-)
I used to believe that movie ratings stood for the following: G=Good, PG=Pretty Good, R=Rotten, X=Extra Rotten.
Now that I'm grown up, I have different thoughts on this.
My twin sister and I used to believe that we could do every dance move the people in Dirty Dancing did. I can't tell you how many times we about knocked each other out when we would try to through a leg on the other's shoulder like they did in the first dance scene.