Joel Jensen: I don't remember any specific 'adults aren't infallible' memory as such, but I very distinctly recall grilling my first grade teacher on the impossibility of Santa Claus.  I wanted to know how Santa got into houses without chimneys.  She suggested that he uses the door.  But what about people who lock their doors? There was no satisfactory answer for this problem, and she kind of trailed off.  Probably my first feeling of being lied to by an authority figure.  Let's be honest, lying to kids seems pretty fun, but if they catch on they'll really think you're a jerk.

Keith Pille: When my second-grade teacher, reading off our options for one of those order-books-through-school catalogs we used to get in class, mispronounced the novelization of Return of the Jedi (she said it “jed-eee”). I'd been convinced that Mrs Andersen knew everything; and equally convinced that you'd have to be some sort of colossal fool not to be down with the Jedi. Clearly, there were gaps in her knowledge. It was all downhill from there.

My father's inability to explain Catholic numerology didn't help much, either.

Don Pizarro: Actually, it happened about this time of year about 27 years ago.  Like other parents, mine swore up and down that Santa would come down the chimney to leave the presents under the tree.  Thing was, we lived in a small apartment at the time and we had no fireplace. We did have a chimney, but it led to the incinerator (this was back in the day when you could burn your own trash).  Sure, they had all kinds of counter-arguments, but this five-year-old knew sophistry when he saw it.

Simon Riordan: Mr. Yuk came to visit my pre-school class to tell us about all the yucky (yukky?) stuff that we should stay away from. After he left, a group of us were gathered together, wondering what the "Yuk-mobile" looked like, obviously green with stickers all over it. A van, perhaps? Like the A-Team? A huge truck? A monster truck? One of my classmates interrupted, "He got into a brown car." I was sorely disappointed by the fact that Mr. Yuk's vehicle was like my parents' car. I was
expecting so much more.

Jonathan Shipley: My daddy's tears.

Amethyst Vineyard: My mom and stepfather got into a big argument over the average temperature in England in the summer, and my Mom went to the encyclopedias to confirm her case, thereby ending the argument. When I looked later, I found that my stepfather was actually right, and my mom had lied about what the encyclopedia had said.