Not one of my own, but...
Some friends of mine had their 4-year-old son tell them that he thought their cat was "a good looker". They wondered where he had picked up this expression. But it turned out to be something he'd just made up, and all he meant was that the cat was very observant.
A childhood belief about speaking

others believed things like this
- As a child I always wondered why I could see everyone else's face and not mine.— Amit
- i used to think that my dad turned into the boogie monster at night if i picked my nose before i went to bed— hollie
- I thought that a person's motorskills meant how good they were at driving!Anon
- I used to believe that when people talked about 4x4 trucks, I thought it meant all the wheels turned.
— tracy - I thought when someone was described as being "mild-mannered" it meant they didn't have very good manners— Samilton Duerheiser
- When I used to see a sign saying "Littering Fine" I thought they meant if you littered REAL GOOD!— Lou V.