Unfortunately, for a brief period of my childhood, I was under the assumption that penguins could indeed fly. By the time I had uncovered my teacher's subterfuge, I had already made a fool of myself by publicly positing that such penguins existed.
Admittedly, my teacher was only playing a prank on me -- but ever since that incident I have been distrustful of penguins. I genuinely hope that one day I can overcome this irrational view and appreciate the flightless birds.