I was taking a shit at the local coffee shop and this dude just kept pulling on the door after he knew I was in there. I eventually yelled "I'm taking a shit. It'll be a few minutes." Like, I can't be the first person on the planet who had coffee/tea and then had to take a shit.
I also had some asshole rushing me when I was on the train to Berlin a few years ago. He was banging on the door and being a complete jerk. I was taking a little while, but, fuck, find another bathroom.
Also remember some poor guy in the Eaton Center in Toronto was throwing up all over the floor... I decided I'd hold it and find a different bathroom to shit in.