I used to believe Monty Hall was a place instead of a man. Let's Make A Deal was before my time and I only knew Monty's name from the Monty Hall problem. I thought "Monty Hall" was the building where the game show took place.
A childhood belief about names

others believed things like this
- Until junior high school, I thought Monty Python was a wrestler.— Jamie
- I thought Hall and Oates was Holland Oats.Anon
- I used to believe that the duo Hall & Oats were farmers. Why else would they name themselves "Haulin' Oats"?— Pat
- I heard the song about Heaven being a place where nothing ever happened and thought, "What a boring place."Anon
- i used to believe Houston was a person, not a place (as in, "Houston, we have a problem") — Kirsty
- I used to believe that flea markets were a place people sold fleas, or the place was infested with fleas— Kelley