My friend used to believe that the lights that tell you when to cross the road were real people that were just really little and were employed to paint themselves red or green, dependng on whether they were "safe to cross" or "don't cross" and then appear when they were needed.
A childhood belief about traffic lights

others believed things like this
- when I saw a sign with a deer on it I always thought deer had to cross the street by it. like a cross walk— only me
- When I was little, I used to believe that deer could only cross the road at the deer crossing signs. — Shellie
- I used to think that "cross-eyed" meant that people had X's for eyes, like dead people in cartoons.— Tim
- When I was little I though "A Cross" was a mud/tar pit and that Jesus drowned.— Usagi Ohkami
- If you cross your eyes, they will get stuck like that.Anon
- I used to believe Nuns are a third gender, a cross between men and women:)Anon