I thought in 12 days of Christmas song that "1 partridge in a pear tree" was actually a cartridge in a pear tree (I didn't know what "partridge" was, so I thought the word was "cartridge" but I didn't know why they put it in a tree), and "2 turtle doves" was actually 2 turtles and 2 doves.
A childhood belief about misheard lyrics

others believed things like this
- I used to think that partridge in a pear tree was "cartridge" in a pear tree(christmas song)— Erica
- I used to think that "mourning doves" were called afternoon doves starting at noon!
— Megaroo - When I was five, I believed God was big as a tree, a tree being the biggest thing I could convieve of.
— Chris - I used to believe that the Doller Tree store was an actual tree.Anon
- When I was a child i thought turtle wax, was to wax turtles.— J.P.
- I used to think that the tree branches moving was making the wind, not the wind making the tree branches move.— Jenny