I'll start.

I had a long time friend when I was a kid. We knew each other because our parents were friends. He had a pet turtle for years, and one day when I was at his house we got it out and played with it and whatnot. Anyway, as I'm leaving his house with my mom, he confronts me saying that I tried to kill his turtle. I had no idea what he was talking about. Apparently the temperature in the tank got put really high up so that the turtle basically would have died from the heat, and he accused me of raising it to try and kill it. That rumour eventually got spread around school and everything, and for years I was "the kid who tried to kill Arron's turtle". :(