1) These quesadillas.
2) When my students write 1x in an algebra problem instead of just x.
3) When girls wear lipstick and it gets on stuff, like their coffee cups.
4) When I spend 20 minutes on the phone with a USC Teaching Assistant that I found on a list of math TA's on the USC website, and finally hire them as a Calculus tutor and then find out that they teach at the University of South Carolina and that I had been on the South Carolina website.
5) When an ambulance goes by and people stay stopped for 10 seconds after the ambulance has come and gone, even though I'm in a rush.