I am glad to know that I'm not unique in this belief.
I too thought that little men were running about inside me (think of miniature Ooompa Loompas). They'd move my muscles, send messages when it's time to dispose of waste (and open the valves when it was time to), handling cuts and scrapes by scurring to the site and putting internal bandages on (scabs), resting when I did, etc.
I thought the sole purpose of my eating and drinking was to keep THEM going.
A childhood belief about general

others believed things like this
- I thought that eating chicken gave me muscles (chicken and muscles sound the same in Mandarin).— NG
- When I was young, I heard the word 'minion' for the first time and thought it was a miniature onion.— Karin
- i used to think there were little mini oompa loompas inside of me that pushed the poop out of my buttAnon
- I thought the phrase "At one's disposal" meant you should dispose of the person or thing.— Geirskogul
- as a young child i thought poo was brown from eating chocolate and pee was yellow from drinking apple juice!Anon
- I used to believe that belly buttons were for putting the salt in while you were eating celery in bed.— David T