Here are some of the videos I've found that show Improv Everywhere's array of amazingness:
No Pants Subway Ride (an annual event!)
I Love Lunch!: The Spontaneous Musical
Frozen Grand Central
These "pranks" are great because they make people think twice. They're art in everyday life. Can you imagine being a bystander in one of these events??
Yesterday, some friends & I decided we're going to plan a mission. Wherever you are, if you want to join up with a group in your city or start your own go here, join the site, and find the group for your location. In the UK, you can also check out this site, & in Bristol specifically go here.
Great, now I have "I Love Lunch" stuck in my head... ;.)