As a child, my mother had the radio on constantly. I used to think that when a song played, the band was actually at the radio station performing it live. Sometimes when a song came on many times per day (i.e. Afternoon Delight - Starland Vocal Band) I used to wonder if they ever got tired of performing that song over and over.
Eric
Cars didn’t move - roads did - and God in his heaven controlled each and every one of them on a huge gigantic Etch-A-Sketch.
A woman got pregnant every time she had sex. When I was about 8, I was hanging out in the living room with my mother while she watched The Honeymooners. They were showing the one where Ralph suspects Alice is pregnant, because of subtle changes in her behavior, but isn’t sure. This perplexed me. If they had had sex, then she was pregnant! Duh! After enduring a few minutes of my confused comments, my mom figured out what I was thinking and said “You don’t get pregnant every time you have sex.”
Capes conferred on their wearer the ability to fly. My mother was making me a Mighty Mouse cape for my 5th birthday, and I was spending many hours fantasizing about what fun it was going to be to fly around the house. Eventually, I made some off-the-cuff comment that clued my parents into my belief, and they set me straight. I was extremely disappointed.
I thought that when I turned toward the wall next to my bed, alien doctors (one of which looked like the band members from the Mos Eisley cantina) would come from under the bed and dissect me.
I thought, but couldn’t prove, that I was a very sophisticated robot, on a Truman-like show.
But best of all, you know those big red and white radio towers? I once asked what they were and was told “They make it so you can get the same radio station at home and in the car.” Somehow I twisted this in my mind to mean: When you turn the radio on in the car, your radio at home turns on with the same station. This really creeped me out, so I lived in fear of those towers.
My dad had a partial upper, and would entertain me by sticking out his teeth. I can’t tell you how many hours I spent with my tongue pressed against my two upper front teeth, in a futile effort to stick them out.
My dad also had a little gadget where you are able to hide paper money inside. Then you take an appropriately sized piece of blank paper and roll it in, and the money would magically roll out. I can’t tell you how many times I tore the house apart trying to find the money machine, all the while feeling guilty that I was planning to counterfeit money! 
I did have monsters under my bed, but only at night. See, at night the floor disappeared and there was a giant hole under my bed. So I had to take a running leap into my bed from the door, because if I got too close, the monsters would grab my ankles and pull me under. Once safely in bed, I also had to pull all the covers up onto the bed, because if they dangled down, the monsters would use them to pull me under.
I also remember a doll (Trissy? Chrissy? Something like that) who had a basic bob. Then she had a hole in the top of her head with more hair coming out, and you could make it be long or short or somewhere in between. I thought that if I cut it off, it would grow back. It didn’t, and my mom was very upset with me.
And it didn’t matter what they told me at school, my parents NEVER did THAT!
I always used to have trouble making the third bump when writing a lowercase “m” in cursive. I remember thinking that if I couldn’t get it right, I was going to Get in Big Trouble for not writing correctly when I was an adult. Yep. Sure…
I thought eggs came out of their shells already cooked.
I thought a wedding was really a “wetting” (as in wet your pants) and used to imagine a giant statue peeing away while folks dressed in fancy clothes milled around.
I thought that the past was in black and white just like you saw on TV. I asked my grandmother once what that was like and when she got to be in color and that’s when I was clued in to the truth.
Obviously, I watched way, way, way too much television as a child.
White kids had to drink white milk and black kids had to drink chocolate milk.
The Boogie Man appeared when a cloud looked like a person. When that happened, you had to run to shade and sing “I’m Your Boogie Man” to make him not get you.
Sheets, no matter how thin, could protect you from monsters, but they had to cover you. The only part of you that could be exposed without enabling the monsters to get you was the lower part of your face. To this day I have trouble sleeping without at least a sheet covering me.
When it rained, the water in the gutter, appropriately called the washy-washy, could be used to wash your hands. The silt at the bottom was called the soapy-soapy. It was also appropriately named.
You could fly if you jumped hard enough. Fortunately, I aimed for the bed when I tested my gliding theory.
I also had an odd idea about how babies are made. I thought that the kiss at the end of a wedding ceremony enabled a man and woman to have babies together. I remember watching one of my mother’s soap operas and hearing about an unmarried couple having a baby, and being confused as to how that was possible.
when i was like, 5, i was watching winnie the pooh and asked my brother what the donkeys name was…being the ever so kind brother he is, he told me his name was Jackass, and me being a niave lil 5 year old, i believed him…until about 3 years ago (im 18 right now)
whenever people talked about winnie the pooh and said Eor (i cant spell his name) i would be like, what the hell r u talking about, his name is jackass, and this would go on and on forever until it was proven too me
i now feel like a jackass and trust me, my brother has paid big time 
My brother believed that babies were made through nipple contact and when I told him the real story, he thought I was lying. I finally got Mom to set him straight.
When my mom would talk about making a Christmas ham, I thought she was talking about that lunch meat that has the red & green (olives & pimentos) in it.
That emergency were pronounced “Emma Gensy” (with a hard G). I would read everything I saw, so in the supermarket:
“Look, Emma Gensy exit!”
Me, as a child, watching a crime drama (mostly going over my head) on TV at my grandmother’s.
One guy on TV calls the other a dago.
My (very Italian) grandmother goes through the roof. “Oh, that’s a horrible word! How can they say that on TV? Don’t you EVER use that word! Don’t EVER let anybody call you that, either!” And so on.
Fine. I was properly impressed. Except the word in question had gone by so fast, I hadn’t really heard it clearly. And so for quite a while, I thought the absolute worst thing you could ever call anyone was ‘dagel’.
For similar reasons I thought for a long time that “fact” was a bad word, which in my childish way I heard and said as “fack”. When I was about four I remember the older neighbor girl from across the street, who was kinda wild, goading me to say 'fu** but I had not heard the word. I said it, but thought I was saying “fack”. I remember saying it in a very small voice, and promptly getting a whack on the backside from my mother. It wasn’t like a real spanking, more like a symbolic spanking to make a point. But the episode must have shocked the bejeesus out of my mother because I almost never got even symbolic spankings.
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I used to watch my parents driving, and noticed the slight corrections they made while driving on a straight road. I thought the way you drove in a straight line was by sort of randomly rocking the steering wheel back and forth. I also couldn’t understand how people knew how far to turn the wheel when going around a corner. I imagined building my own soapbox racer, but pasting photographs of the front wheels around the steering wheel, with each photograph lined up with the proper position of the steering wheel to obtain the desired amount of front-wheel turning shown in the photo.
I also asked my mom how she knew when to shift gears. She said she “just knew”. Wasn’t a very satisfying answer.
The first time I saw the tv show “Lost in Space”, I wasn’t old enough to understand plots and characters, so I thought Dr. Smith was the good guy, and everyone else were the bad guys. Same with “MAS*H” - I thought Frank Burns and Hot Lips were the “good guys”.
For (too) many years I thought that sanitary napkins went “the other way around”, instead of the glue sticking to the panty, that it went the other way around… I never gave it much thought until I saw a commercial for the ones with wings, which did not make any sense. That’s when I asked and was told the truth.
Also, when I was frightened by a horror movie, of any kind, I would just convince myself that it was OK since that “kind of stuff only happens in the United States” (since all the horror movies I was exposed to happened in the US) therefore, I was safe. The problem came when we traveled to the US (many sleepless nights as a tourist ensued).
Lothos
Oooh, that reminds me…
In kindergarten, someone at school told me to say “goddamn” but I heard and repeated it as “God dim.” My teacher overheard me and, without explanation, made me sit in the principal’s office for the rest of the day. I finally found out what had happened about seven years later.
Okay, slightly embarrassing, but when I was around 5 we had a black housecleaner who was very nice but I somehow had it in my head that if she touched me my skin would turn black in that spot. I have NOOO idea where I got that notion but remember always keeping a minimum distance between us.
And there were monsters under the bed who would most certainly grab any hand or foot unfortunate enough to dangle over the edge like so much bait.
And I couldn’t bear to have the closet door open just a sliver - had to be completely closed or else there was something in there watching me and waiting to pounce.
Yikes!