its funny to slow down and say hey you dropped something madam or sir then wait for them to go pick it up and yell something like your dignity or something along those lines
Used to drive around doing this shit constantly, but none of this remotely acceptable shit. Just bile and awful nonsense. Usually accompanied by a sever trash can running-over. (A certain unnamed then-future Vital singer was a frequent participant in this, which was about as hilarious as you'd imagine.)
