1. ...It is expected
A woman buys white coat she has been saving up for for ages. She tells the shop keeper she has dreamed of wearing it for months and been saving up. The shop keeper says that this is the last one in stock. We see the woman's gleeful face as she tries on her new lovely white coat.
We cut to a scene of a park keeper painting a bench black... oh and let's really overstate it... he's painting the bench black by the zebra enclosure in a zoo. We know what's going to happen already. The comedy is in the anticipation and expectation as we build up to the inevitable moment where she sits on the wet black bench in her new white coat and ends up with black stripes across her back.