I met a girl back when I was 18 and really hit it off with her. She told me that her ex was scary because he punched his dashboard when he was pissed off. Her ex was a guy on the fringes of our social group, so I didn't know him well.
A few days later we're in bed and my roommate lets her ex in. He confronts us with a major "WTF?" Apparently she never bothered to tell him she was leaving him.
A few weeks later, she's gone on to someone else and I'm best friends with the ex. We're still on friendly terms decades later.
I met this kid in my early school years, nearly 40 years ago. We were in the same class, and we became best friends. This was a whole lifetime, state and gender ago, and for some reason, we're still friends :)
I was new to a school and decided to skip class with a bunch of classmates I barely knew. One guy goes to the bathroom and comes back and stands right behind me. I look up and he is completely naked except for a sock on his dick hovering right above my head.
We've been great friends for close to 18 years and I just got to meet his two kids.