Demonstrating water boarding torture to people passing by to protest the US atrocities in Guantanamo. Done in a fun an kids friendly way, but with a pretty grim agenda underneath.
There is nothing more effective than to have people laughing while they think about a serious subject. It is so easy to make art and activism, that makes people angry. But getting people to smile and think at the same time is much harder - But also much more efficient in changing peoples minds.
Angry people have frozen minds. But smiling, laughing people are open-minded and ready to change.