This group put me very much in mind of Mata's group's fun.

http://www.improveverywhere.com/

I personally liked the time loop and started laughing over the home depot mission.

That's fantastic! I wish there were more things like that around the world.

Happiness is a silly idea acted on by a couple of hundred people. (Although war is a silly idea acted on by a nation.)

I love them! I wish I could take part in something they organised

I've heard of two similar things mentioned on the forum that happen in England.

The mass zombie appearances.
The massive water fights.

Too lazy to go search out the web references but both seem to be in the spirit of harmless fun.

I'd argue the famous Tomatino tomato fight is another (now probably quite commercial) example.