When I was little, I was told that on movies and shows, the actors were just playing a game, and later went home, and had regular lives like normal people.
My logical, though mistaken, assumption was that when cartoons were over, cartoons went home and had regular lives. The reason I never saw cartoons anywhere was because they lived in a separate cartoon world.
A childhood belief about tv shows

others believed things like this
- I thought cartoons were real, I remember asking my mom why there were lines around the "actors" in a cartoon.— Steven Graziano
- I used to wonder why people didn't have outlines like they did in cartoons.— Anna
- I used to believe cartoons were real people and animals. They were just wet.— Wendy
- I used to believe cartoons where real people. You can imagine how that went... — Emma
- When I was a kid I used to believe that cartoons were people dressed up in special costumes.— Sarah-Jane
- I used to think that "cross-eyed" meant that people had X's for eyes, like dead people in cartoons.— Tim