I went to a wedding where the sister of a good friend of mine was getting married. I'd hung out with the groom a few times before, he was a nice dude but super quiet and never drank, so he never quite fit in during our poker games or general shenanigans.

At the wedding when I met the groom's dad I finally understood why he was the way he was. The dad was a huge guy, very rough around the edges and an alcoholic. Him and the grooms mom were separated, and during his speech he talked about how the groom was conceived, how hot his new daughter in law was, and generally called his ex wife a slut and bitch a lot.

My friend's dad (father of the bride) tried to put a stop to the speech several times but was pushed aside. Finally after about 25 minutes he stopped and started threatening and trying to fight anyone that was giving him a look. In the end we called the police and they hauled him off.

Whenever I think of their wedding day (they're still happily together and have a kid now) the first thing that comes to mind is that speech and the aftermath. What a terrible way to remember what should have been a special day.