Hee hee, I am reminded of a time when we were playing a Star Trek game, and the person playing the first officer had to go to the bathroom, and the guy playing the Captain said Number One, take care of Number Two!

And we all died laughing.

Maybe you had to be there.

In the States there is a raging trade in blame-the-other-state; in Arkansas, a knife is a Texas toothpick, and so on.

Other euphemisms for peeing include:

See a man about a horse (this one I really don't get, must date from the wild west times or something)
Drain the main vein
Recycle my beer
(After all, you don't buy beer, you only rent it!)