Some of these are so funny. Almost makes you want to have (more) kids just for the entertainment value. Almost. There’s always grandchildren.
If I revved my batter powered toy car backwards, would it recharge its battery?
I wondered why the Post Office had a big “Post No Bills” sign. Where else would you mail your bills? would you get kicked out for mailing a bill? If you put your bill in the mailbox, would it get rejected by the post office and returned?
It was all such a mystery.
Most of the things I recall wondering about were science-oriented, and generally not odd enough to be of much interest here.
One pretty out-there pondering I remember is spending quite a bit of time wondering what would happen if things could move through time at different rates. (Not in the relativistic sense I’d learn about later, but objects close together in the same frame, with changing speeds.) I spent several days thinking it through, doing odd little experiments, and scribbling. I eventually concluded that it would probably be rather dangerous if the differences were very big.
“Do you have any idea how hot a light bulb gets?”
I went to a Presbyterian church as a child. Right outside the church was a bus stop. At the bus stop was a trash container that said “For Pedestrian Use Only.” I guess they didn’t want drivers emptying their litter bags which had just started coming into use.
In any case around age 6 I began to wondered why my church didn’t want any people who went to other churches throwing out their trash there.
Where did the sun go when it sets? Was there, like, a big hole in the ground or something?
Also, my child’s mind thought of church as being basically a theater production, and I couldn’t understand why some people thought it was so important, or why it was the same thing every week, or why some people went to one production all the time and other people went to other productions.
Mine was the Mutual of Omaha jingle they played on Wild Kingdom: “Mu-tu-al of O-ma-HA is peo-ple… you can count on when you’re gonna interrupt.”
What, were they going to come up behind you and put a hand gently on your shoulder so you didn’t?
Thought of another one: I was listening to a record and reading along with the lyrics on the sleeve, and I wondered whose job it was to listen to songs, figure out what the singer was saying, and write it down.
When packets and recipes said ‘salt to taste’ that really confused me- I could always taste it without salt, couldn’t everyone else?
Was that my superpower? 
If I ever have a kid, I’m telling him that when he flushes the toilet, it all goes to Poughkeepsie, and that there used to be a Peekeepsie which handled #1 separately, but because of budget cuts in the 90s they had to shut it down and Poughkeepsie has to keep everything.
No, no, no, pee goes to Peekskill.
I used to get so confused with drug stores. I mean, drugs are illegal, and they have a huge sign saying that they sell them. Whenever my Mom went into one, I thought she was being bad and the police would come.
Heh, don’t feel bad. When I was a kid I thought the purpose of salt was to cool off the food. Mom would put the piping hot food on the table and everybody would grab the salt and go to town.
I always wondered how did my parents drive from point A to Point B and then back to Point A again with out getting lost. They’ve made like a hundred turns between point A and B. How the heck did they remember exactly where all those turns were?
Somebody want to explain this one for the young people?
Mutual of Omaha is an insurance company that was the sponsor of a TV show called Wild Kingdom hosted by zoologist Marlin Perkins. As the only sponsor, they of course had their jingle at the beginning of every show, so that the viewing audience at home would know they were people you could count on when the going gets rough.
Just like your non-brothers and sisters did. 
d&r
Easy. The sun sleeps in a big bed just beyond the horizon. Then it wakes up the next morning and reappears in the sky.
“Waitaminnit!” you ask. If the sun sleeps all night, how does it get back to the east the next morning? I was ignorant about directions when I was a kid, so it just made sense that it rose in the same place it set.
I could not for the life of me figure out how the turn signal knew which way my mom was going to turn. It always started clicking, and sure enough, the little green arrow started flashing a few seconds before she’d make a turn, and SHE’D ALWAYS GO THAT WAY!
Hypotheses included that we took the same routes so frequently that the car somehow got programmed.
I even asked, and, not realizing I couldn’t see her flipping the lever from my carseat, my mom was thoroughly perplexed as to what I was asking.
I wondered why at Easter time every year they played the 10 Commandments. I thought it was because all of the Jesus movies are really bad movies.
I remember that too, but it even lasted until I started driving. I had no clue how to get anywhere as someone else always took me - I never bothered to pay attention. As soon as I got my car there were places I wanted to go - and I had a general sense where they were, but it took me a long time to get there. I knew when I was on the wrong track - as things looked unfamiliar, but didn’t remember turn here or turn there just - there was a McDonalds on the way or a big church on the left hand side.
I also remembered having a concept of the world as being pretty small. We had power lines a couple streets over. Somehow I had it in my mind that that was where all the TV shows came from. I thought of the world as pretty much just my neighborhood and the roads up to where my grandparents lived.
I remember beig confused about things - when somewhat older - like OTC drugs. I figured there must be “under the counter drugs” - and at our drugstore - there was a counter, but no space to slide something under - and why would you do that anyway.
My great aunt (quite a character compared to my other relatives) had a mug that said “bullshit” on it. I knew what bull was - and I knew what shit was, but I couldn’t understand what the deal was with them put together or why anyone would want a mug with it - not sure I still do…
I wondered why my parents kept letting us get pets, but then would later claim we didn’t have enough room and they would send them to some mysterious farm to live…