Pigeons on the N.
I file this under the "accident in slow motion" category, where you are not quite sure what it is you are seeing, and by the time you figure it out, the window for the appropriate reaction is long closed.
These pigeons were very cute, walking up and down the isle. It wasn't until we were nearing the station that I started to worry they would get trampled. But instead of getting trampled, when the car filled up, they hung out under a seat. People didn't even know they were there.
They traveled all five miles from Folsom and Embarcadero to Carl and Cole, possibly beyond (that was my stop).