One day when I was about 7 or 8 my guy friend from across the street came over. He was always bragging about anything he could think of, so one day I told him I could speak Cherokee, he asked me to prove it and I just blurted out some random made up words. My dad had been BBQing just a few feet away and when I stopped "talking" he said "Pretty good Cherokee sweetie."
After that I had completely convinced my friend that I could speak Cherokee, and my dad had convinced me that I could too.
I was about 11 when I finally figured out that he was kidding.
A childhood belief about speaking

others believed things like this
- I had my wife convinced that Steven Hawking made his fortune as the original voice for the speak N spell toy.Anon
- I would speak in gidderish, convinced that it was some foreign language I had never heard of— Molly
- a friend was convinced that his school was an asylum, and couldn't be convinced otherwiseAnon
- My friend convinced me that if I used a bar of soap to wash my hair instead of shampoo that I would go bald.— Michelle
- When I was a kid I was completely convinced that Sade's "Smooth operator" was "Ooh of the red eye".— Brookstar78
- when i was a kid i used to believe the monkey could speak— killian