They are, more or less, a combination of street theater and guerilla improv. They go to places and "cause scenes" that are strange, amusing, or just plain surreal. But the cool thing is that they aren't trying to make fun of or take advantage of anyone. They just want to add some fun to people's lives!
This is a philosophy I can totally get behind. I'm very much in favor of that sort of friendly surreality myself. (And, I think, anyone who's played minigolf in a fursuit would have a hard time arguing otherwise.)
Out of all their "missions", I think that The Moebius is my favorite. A group of eight performers, looking like normal patrons, go into a Starbucks. They then proceed to exactly repeat their own actions every five minutes. For an hour.
Brilliant. Another good mission is Ted's Birthday. The world needs more surreality!
Thanks to auroralockwood for pointing this group out to me.