There were all the normal ones.... santa, easter bunny, etc...
It wasn't the first, but it was certainly the first time I ever realized "I've been lied to!". Story time:
It was in the early fall of 6th grade. And bear in mind, this was back in the days before Kazaa and Morpheus and all the internet "resources" we've come to know and love. My friends and I were sitting in the living room of my buddy's place. We'll call him David. Now, in my area, the schools do the "puberty talk" in 6th grade and so, like any other middle schooler we were uh... studying for the class. Of course this was all new to us and at that point the sight of a pitted avocado was good enough for any one of us. So we were amazed at all of the wonderful things we were finding out about the fairer sex.
Dave's parents werent home at the time but his older brother, John, was. He knew what we were doing and mostly ignored it, but after a bit he came in to check on us and tell us that "Just so you know, the workbook doesn't say anything about it, but if they ask you on the test, Asian vaginas are sideways. [as in, running east-west, not north-south]" We all nodded in understanding.
Well fast forward about 2 years... it was summer between 7th and 8th grade. I was at another friend's house and we had managed to find his dad's collection of Playboys, Hustlers and some other nudey rags. It was a treasure trove, I'm telling you there must have been 200+ magazines. This was the first time I ever saw porn. And the first Playboy I found had an Asian centerfold (wish I could remember which one but it's been so long now). And I was of course amuzed, but then it hit me... her vagina isn't sideways! I'd been duped! Tricked! Lied to!
My buddies pick on me to this day about that, but Dave's brother had me hook, line and sinker.
TL;DR: Buddy's brother had me convinced Asian vaginas are sideways. Took me two years to figure out I'd been lied to. Never lived it down.