I used to believe that the cows owned by my grandfather slept lying on the ground like a human at night.
I thought "carrot and the stick" meant laying a carrot out on the ground in front of the horse (which it'd walk towards) and laying a stick on the ground behind the horse (which it'd walk away from because it would hurt stepping on the stick.)
And I wondered, why would stepping on a stick hurt a horse?
I used to think that when a baby bird was old enough to fly out of the nest and live away from the mother bird, it would sometimes go back to back to visit her in the same tree, like when we humans stay in touch with our relatives!
I used to think that when female animals got pregnant, they sometimes didn't need a male partner (I was thinking of cats when I said out loud) and could somehow just make babies on their own. Well domestic cats are usually spayed or neutered anyway, but even so!
A kid at my summer camp told me that a black widow spider was the size of a house and that you needed a hundred bullets to kill one.
I once for some reason thought a Mantis was a bird, instead of a bug...
I used to believe that a butterfly and a moth were the exact same thing. I thought they stayed at butterflies in the daytime and transformed into the moth pattern when it became night time.
OK, so there's this book called The Lion, the Witch, and the Wardrobe where a magical lion named Aslan is killed but comes back to life.
When I was a kid, I thought that the reason was because he had nine lives.
I use to believe the fireflies were birds with spotlights
I used to think mouse is really green.