I had just gotten in the car with my brother, sister and some friends after eating a ton of food at this seafood buffet. I felt my tummy rumbling as we were walking to the car, but I didn't wanna hold everyone up by going to the bathroom and I figured I could hold it til I got home. It was about a forty minute trip and I almost did make it. As my brother was driving I kept saying I need to go and asking him to stop somewhere because I didn't think I could hold it, but he just kept driving faster and faster until he was pulling off at the highway exit closest to our home. I had been holding it with all of my concentration and strength, but my sphincter just couldn't go on any longer and I shat myself right then and there in the car. I think everyone assumed I was exaggerating about needing to take a dump so urgently, but a few seconds later when they smelled what I had struggled to save them from smelling they knew how wrong they had been. In my head I always thought people shitting themselves had solid poo, and at this time I realized how that defied logic. You can always hold solid poo, but holding water/diarrhea is a lot harder. They had to roll down the window to get some breathable air in the car and it was wintertime. As we pulled up to the house I ran to the bathroom with diarrhea dripping down my legs and soaking through my pants and I even got some on my socks. Luckily, none of it was in the car, so they just aired it out for a few minutes. Since my bro had driven so fast we got to the house first and only a few people witnessed the incident. As far as I know the four of us never spoke of it besides while it was happening. We ended up going out and partying that night after I got cleaned up and I have been very careful about staying close to a toilet if I'm not feeling well ever since then. Tldr: shat myself in front of friends and family on the way back from a big dinner. Everyone took it in stride.