You know that cartoon Digimon? Well, I used to believe that me, my best friend, and a few other kids we knew were really Digi-Destined, and someday, we were going to go into the Digital World and have to save it from evil. We "knew" who our Digimon were going to be because it had been psychically suggested to us, and at one point we were even convinced that we were taken into the Digital World when we were younger but made to forget about it. It went so far as us to assume that we would occasionally get "possessed" by our adversary Digimon, MegaTyrannomon and occasionally DarkMistressmon. We were convinced it had to be us because we also happened to be sorcerers (obviously), because we knew "magical artifacts" (usually bizarre yardsale knickknacks) when we saw them.
We thankfully grew out of this, but I'm still not entirely certain about one of those "artifacts" that we called the Stone of Chaos. It really was creepy...
A childhood belief about cartoons

others believed things like this
- Even though I knew about Roman numerals when I was younger, I thought that there was 11 world wars.Anon
- I used to believe that I was the only person in the entire world who knew about my favorite ratio station.— Gillian
- I used to think everyone in the world knew and thought in English, but choose to speak different languages. Anon
- When I was a kid I was convinced that the world would end by a nucleur explosion. — Marshall M
- My older sister had me convinced that noodles grew on trees, but that rice was man-made...— Trusting little brother
- As a little girl I used to think that the world was magical.Anon