Pretty common belief among stupid 7-year-olds, I think; humans couldn't see colour up to the mid-60s.

That there were little gnomes inside the doors of the cars and that they were in charge of raising and lowering the windows, especially in the automatic cars.

I thought every song on the radio was being performed live somewhere

The semaphore homunculus lived in the stop lights at intersections.

In my Superman onesie (w/ cape), I could fly, but was never brave enough to launch from a high enough step on the stairs. I knew I was flying, but...

I thought adults were smarter than me

I thought those crosses or flowers on the side of the road were where they buried the person who died in an accident.

I believed I was an adopted alien from outer space before I realised my face is like my father's but prettier.

I used to think a car direction indicator was a GPS guiding system, and not manually operated.

Americans/Canadians made out while they undressed before sex, like in the movies. English people calmly undressed in front of each other and then began having sex in a dispassionate and business-like fashion. I think some other kid heard an adult say it as a joke then passed it on as a learned truth.

For a while, I thought kissing was how women got pregnant.

It MIGHT have had something to do with getting a half sibling in spite of my father saying he hadn't had sex with the mother. Religion makes people weird, is it really that big a deal to admit you had sex out of wedlock, when everybody already knows you got someone pregnant?

That we would live in peace

Can I'll cheat a little and use my teen years.
When let's plays where the new hot thing, I thought a blind let's play literally meant, eyes closed

I thought that the Michelin tire company was headquartered in Michigan, USA and not France. In my defense, most of the US auto industry is based in Michigan, and they sound similar.

Also: I will never accept the "fact" that the Michelin Man is named "Bibendum"

That tv programming would pause when I turned the TV off.

Two that come to mind:

People would say that's an "old timey" car or something and I thought that was a brand name.

I thought the people who had really tall spiky mohawks had hair that just grew like that.

rice turned water into soil

Cthulhu is a Hindu god

Freddy Krueger was two people. I thought it was like Dr. Frankenstein and his monster. I thought it was Dr. Krueger and Freddy was the monster he created. When I saw the movie I was like where's his creator, the one that brought him to life?

I used to greet clothing store mannequins and thought that people who didn't were very rude.

that you're supposed to show a middle finger as if you were showing it to yourself