My wedding wasn't exactly a shit show, but there were a few unexpected hiccups.
First, we made the mistake of having my dad officiate the wedding. My dad is a pastor, but my wife and I aren't religious at all. I didn't grow up religious either, and my parents didn't become religious until I was out of the house, but we love and support them so I wanted him to be a part of the wedding in that way. I don't know what I thought he was going to say, I assumed there would be religious undertones, but this was a full blown self indulgent sermon that lasted forever. My parents aren't aware of our religious affiliation (or lack of) either, as I don't think it's a completely necessary for them to know. I did get into an argument beforehand after asking him to omit "marriage is between a man and a woman as god intended" as I felt that was completely unnecessary and preachy (and my wife and I don't share that belief).
Other than that, my brother who was my best man, bought the wrong color shirt. We had a specific outfit that we asked everyone to purchase - no tux or anything, we just sent links to the groomsmen for the shirt and pants they should buy, and somehow my brother ended up with the wrong color, and we discovered this the day of the wedding. Thankfully, one of the other guys in my party who was the closest to my brothers size somehow ended up with two shirts because his order was messed up. So that was a really minor hiccup that could've been much worse. This was partly our fault because we should have checked if everyone had the right outfit before the day of the wedding.
Finally, I pissed my pants 20 minutes before I walked down the aisle. We had an outdoor wedding, and my nerves were kicking in, and so I relieved myself next to a barn. I underestimated the duration of my piss, and threw 'er back in my pants prematurely without shaking it off. Had a definite spot running down my thigh. I spent the next fifteen minutes furiously trying to rub the spot out of my pants, periodically glancing up at the sun as if I had the ability to command it to dry my pants faster. I managed to get the spot out just in time for me to walk down the aisle. So not quite a shit show, but a lot of bullets were dodged.
TL;DR My dad sprung a 40 minute unexpected sermon, my brother almost wore a different colored shirt, I peed my pants.