In a game of tennis, when the umpire announced the score as Deuce, I used to think that he/she was telling the players that it was break time and they were welcome to some "Juice" to drink!
A childhood belief about sport

others believed things like this
- I used to think that apple juice was beer and I'd drink it all the time and pretend to be drunk.— Dee
- I thought that grape juice was called "great juice". Anon
- I thought the song "Little Deuce Coupe" was "Little Loose Tooth".Anon
- 'To Be Announced' in the TV guide was a film that was on all the time!— Clare
- I forgot the expression "not cricket", so I said, "not tennis" instead.Anon
- I used to believe that the game The Legend of Zelda: Twilight Princess was the longest game ever.Anon