My parents own a very skinny tiger cat named Kaboodle, and my brother's family has a very large Golden Retreiver named Buddy. While babysitting the other day, my 4-year-old niece announced to me, "I don't think Kaboodle is Buddy's mother". I did some investigating and found out she got this from her older 9-year-old brother, who now at this late age has only just learned that cats don't give birth to dogs! :)
A childhood belief about cats and dogs

others believed things like this
- I used to think Buddy Rich was called Buddy Rich because he was my dad's friend, same with Buddy Holly. Anon
- My 18 year old brother thought the former vice president was named Al Gorbachov.— Jeff
- My buddy used to think that when Steve Millers sang "Jungle Love" he was actually saying "Chug-a-lug" — Harold
- I thought Kaa's name from The Jungle Book was spelled "Car" and that he had a brother named Truck.Anon
- Since lions and tigers are larger versions of cats, I used to believe bears were large dogs— Chris Ayala
- My mum told my older brother that dogs weren't allowed in London.— Fiz