Improv Everywhere is an amazing comedy troupe in New York City. I just found them the other day through a link at a webcomic I read. The videos and Agent Reports keep me laughing pretty much constantly. If you decide to visit, know that it takes some time, but it is well worth the entertainment.
I wish there was something like this here. If there was, I would totally participate.
Cheerios, the Crunch, and the Crunch Town Flakies,