This site might be of interest to readers of this thread:
In the late 60s I was about 6 years old I was with my father on the way to go fishing, but he said he had to stop at the power company to pay a bill “or else they’ll come and turn off all of our lights”.
The first thing that popped up in my mind was this big black sedan screeching up to our house, then several black trench-coated, stern faced men burst in the house, wordlessly fan out and turn off all the wall and lamp switches, and then leave.
Ah, sort of the opposite of my childhood friend, John Athan.
I used to believe that two people were related if they had the same first name. I have an unusual last name, and anyone else who has it is related somewhere down the family tree, so it just made sense in my kid-logic.
Mom used to make beans, the red ones with the white center. I used to think that the white center was mashed potatoes and I couldn’t figure out HOW they would stuff beans with mashed potatoes.
Not me, but at camp there was a guy, about 12, who was convinced that his UFO-visitor comic books were telling actual true stories. I had to point out the “fictional stories” notation at the front of the comic.
I used to think that Germans were bad people.
Obligatory Simpsons clip:
I went to to Presbyterian Church as a youngster. There was a bus stop on the corner where the church was. There was a small trash receptacle there that said for “pedestrian use only”. I thought it said “for Presbyterian use only”.
I heard about older adults getting shingles. I thought that meant they grew roof shingles out of their skin. I was about four or five and we were also getting our roof repaired. 
When I was a kid, I thought that a “birthday suit” was an extra fancy suit of clothes you wore to celebrate your birthday and I kept wondering when I would get a birthday suit of my own.
Same here, thanks to this book:
As a very young child, when I first learned that America had to fight for its independence from England, I had a mild anxiety for some time that the English were going to try to take America back at the first opportunity. Before that whole “it was nearly two hundred years ago and lot has happened since then” sunk in.
On another note: while watching one of my fave Youtubers do a mukbang (briefly, two or more people have a conversation while sharing a meal, sometimes commenting on the food they are eating but not necessarily so), I remembered that this was what I thought happened during a Dean Martin Celebrity Roast. I never watched those shows until at least my teens, so as a young child I just saw promos and drew my own conclusions.
Did you think the celebrities were eating roast beef?
Well, that’d be better than being served a Dean Martin Roast…
(pickled meat as a roast? No thanks)
It is not pickled, it is marinated.
Hell, I’d be afraid to let that much alcohol near an open flame…
They weren’t afraid to let the celebrities smoke.
I used to think my Dad could control the traffic lights. We would stop at a red, and my Dad would say “Lights changing in 5,4,3,2,1”, snap his fingers and ‘Wow!’ Every time.
What he was doing, of course was watching the lights of the cross traffic and knew the time gap between the cross traffic turning red and the through traffic (us) getting a green.
(It’s also possible I may have tried this same trick on my children).
I was driving forklift in a warehouse when a goofy salesman from up front asked me how to open a big overhead door to get into the rest of the warehouse. I told him to say “open sesame”. When he finally turned and said it, I punched the button that just happened to be on a pole next to where I was idling.