I've long been a fan of Improv Everywhere. Their work does volumes to illustrate why cities are such interesting places.
One of the basic city behavior principles that they illustrate is this: When one person does something it can be creepy. When everyone does it, its A-OK!
The perfect example? Pantsless subway riding. This has long been a tradition in New York, and this year has taken hold on our very own TC light rail.
Warning: Don't try this alone. You're liable to go to jail.