What happens when two armies of thousands go head-to-head in the most epic water gun fight? Fun happens, that's what:

This MP3 experiment is an annual public participatory event organized by Improv Everywhere. This year's event saw 4,000 participants who were given the task to download an original MP3 before meeting up at a specific location. What followed was 45 minutes of syncronized, hilarious antics which was a mix between a scavenger hunt and a flash mob.