I used to believe that everybody around me were aliens in human guise and that they were conspiring to take me with them, and "alienate" (in that other sense) me. I also thought they could read my mind, so I tried to blank my mind whenever I saw anyone staring at me suspiciously. And yeah, that included my parents and my big brother.
A childhood belief about aliens

others believed things like this
- When I was little I would always say in my mind, "I know you can read my mind", just in caseAnon
- I used to believe...If you ate sunflower seeds you could read somebody's mind...LOLAnon
- For the longest time I was sure my cat could read my mind.Anon
- "Going to the jazz club in my mind"? Not me! "Going to Nebraska in my mind..."— Felix
- When I was a kid I used to believe that my perent's were aliens and I was the only human in the house.— Ali
- I didn't mind eating lambs brains when I was a kid because I thought it would make me smart.Anon