I've done it twice, once was in my mid 20s when I had food poisoning and lying in bed. My boyfriend and I had had a fight during the dinner that gave me the food poisoning and when we were in bed later still a bit mad, I wasn't feeling good but trusted a fart and shat myself. I was pretty embarrassed but he immediately forgot he was mad and took really good care of me while I puked and shat (in the toilet at least) for the rest of the night.

Then I did it again last year in a gas station bathroom. I don't have a great excuse for this one except that we were on a long road trip and I really had to go so I went to a gross gas station washroom but then while I was doing my poo my mom kept knocking at the door panicking cause I guess she really had to pee. I felt like I finished so I wiped up, got up and was washing my hands when I trusted a fart. Thankfully I had a change of clothes in the car or else I would've had to sit in my own shit for the next 3 hours.

I'm suspicious of people who say they've never shat themselves...