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 childhood belief about cats and dogs

others believed things like this
- My sister and I thought cats and dogs were the same animal, the dogs were male and the cats were female.— Paul
- I used to believe all dogs were male and all cats were female. I still call dogs "boy" and cats "girl." — Kelly F.
- I used to believe all cats were female and all dogs were male.— Sabby
- I used to think that all cats were female and all dogs were male. — Annalisa
- i used to believe that all cats were female and dogs were male!Anon
- I used to believe that cats were all female and dogs were all male.— Rachel