One day this is going to go horribly wrong, crazed by their own power Improv Everywhere will send their legions of order following hipsters on a murderous rampage across US cities.
Luckily that day was not yesterday. Instead they got people to tidy up New York stores, give out cheerful high-fives and hold a surprise birthday party.
More than 3,000 people took part in 'The MP3 Experiment Seven' where they all simultaneously followed recorded audio instructions.
After gathering in a selection of New York stores they all pressed play on their MP3 players at the same times and followed a series of directions.
You know the drill, they stand still, people without headphones look confused... it's really probably better if you just watch the video.