What childhood myth did you believe for way too long?

[Casler1]

We all know the standard childhood myths, but what is something you believed was an absolute factual reality well into your teenage years (or worse, adulthood) before the bubble burst?

Maybe it was a blatant lie your parents told you to keep you behaving, a total misunderstanding of how the world works, or a movie trope you thought was a real law of physics. Drop your most embarrassing 'wait, that's not real?'

Mine is Santa Clause until I caught my dad sneaking the gifts when we are asleep.  lol 

[AleksandarMe]

Mine was the Tooth Fairy for sure, i caught my mom putting cash under my pillow one morning.

[Robynator]

I always felt like all the mythological creatures from greek to roman and also Egyptian was based on something that really existed on earth at some point, i was wondering how different society trough different time has the imagination and creativity to invent extraordinary story and character like that.