What is it about cats and sinks anyway?

Just for those who find this sort of thing unbearably cute.

This site of course doesn't go into the dark side of the cat-in-sink phenomenon- I remember the times I've been about to do my business, turned around, and there has been a cat looking at me from a sink with polite interest. And they always get so miffed when I usher them out the door- they have sort of an "Hey, I was here first!" expression.

I'd be annoyed if they wern't so cute.