When I was around 5 or 6 I invented myself an imaginary wife named Sonja, and I told everyone about here and had a whole pretend life with her. At that age, I only knew one phone number besides my own (that wasn't an emergancy number), that played a recording of the local weather forcast. I'd call it and have made up conversations with her. I think the imaginary marriage lasted a couple of years before I abandoned the fantasy.
A childhood belief about imaginary friends

others believed things like this
- I used to have an imaginary friend named Mr. Nobody. He would protect me from my imaginary enemy, Bad Elmer.— Kdees
- when i was little i believed that your social security number was the number you were born on the earth — christine
- when i was growing up i had two imaginary friends. One was named Jennifer, the other was named Onion.— Tessica
- I thought weather forecasters were psychic and that's how they knew what the weather would be.Anon
- When I was six I had an imaginary friend named Binky. When I was seven my dad ran over Binky with the car.— Shadia Granger-Malfoy
- I used to believe there was a number "eleventeen". I could never quite work out where it went, though.— Matthew