When they fight over stupid things.

I had married friends

*looks at phone, pretending to send texts*
*Awkwardly pets dog/cat/bird/houseplant*
*Dent in the wall suddenly becomes very interesting*
*Pretends to get a phonecall and moves to another room*
*Takes a bathroom break. Stats until the sounds of arguing are over. Blames "the tacos/burgers/lettuce" I had last night*
.
...And then they drag you into it...

I see a theam in your posts

I told you people, never subject yourself to being the third wheel.

If you ignore that, this is when you leave and go home.