There is a group in New York, called Improv Everywhere and they do the most funnest things ever. If I lived in NY I would totally participate in their improv pranks.
"improv Everywhere is a New York City-based prank collective that causes scenes of chaos and joy in public places. Created in August of 2001 by Charlie Todd, Improv Everywhere has executed over 100 missions involving tens of thousands of undercover agents." –from the website.
I could post all my favorites but that would be a long long email. So I posted this TED video, to see the story behind Improv Everywhere. I think you will laugh.
So enjoy and don't forget to play hard, and enjoy life.