I was sitting by the window on the bus, a Hoppa, with a low floor, and as we were driving along, the driver opened the doors.
We were passing a young black guy, who was cycling parallel to us at the time, looking fairly chilled and smoking what looked like a reefer. I thought the bus driver must know him and was going to shout hello, but instead he shouted:

"Hey, pull your pants up, you can't ride around like that!".

I looked over and his shorts had fallen right down, and he was showing his arse to the world.
He grinned and pulled them up with one hand as he cycled along.

Everyone on the bus stayed stoney faced but it really made me laugh.