I thought that "foul play" had something to do with sex. Maybe I got it confused with fore play?
A childhood belief about sex

others believed things like this
- I thought god looked like the face on the play-doh can!— Jonathan Franz
- My parents used to have an old radio. I thought it could only play old songs, like from when they were young.— kathy
- I used to believe that my toys would wake up when I went to sleep, and would play by themselves.Anon
- I used to believe that you could only play a record once, and after that all the sound was wiped off.Anon
- I used to think that babies were born with clothes and maybe a little play toy— Shauna
- I used to believe that if i swallowed some Play-Doh and made a wish, my wish would come true.— Nadia