I grew up in the New York City area, where there were at least two teams in each of the major professional sports leagues (MLB, NFL, NHL, NBA). Because the Yankees and Mets in baseball were in different leagues and never played each other during the regular season (and never did until just a couple of years ago), as a little kids just starting to discover sports, I thought that was how all the New York teams in all sports were set up. So the Rangers would never play the Islanders, the Knicks never played the Nets, and the Giants never played the Jets. It just somehow made sense that way, and I was probably around 15 before I realized my error.
A childhood belief about sport

others believed things like this
- I used to believe that invisible giants played with us like I played with my dolls. — Alexandria
- I used to believe that the "real" Santa Claus was at Macy's in New York City. All the rest were fakes. — Marcia
- My mom used to believe that the San Francisco Giants baseball team were actual giants.Anon
- my sister told me that bunkers on golf courses were for children to play in while their dads played golf.— Julie
- When I was 5 years old I tought it would be a nuclear war every time I'v played with playmobil.— Sgt. Miller
- i thought that all of the shows on tv where played live even when someone died. sad, i no.Anon