Those walking through the +15 near Bankers Hall around lunchtime may have been surprised by some crazy colours and spontaneous moon-walking, singing or people falling to the ground.

Improv Everywhere, in cahoots with High Performance Rodeo, got up to their annual outrageous public pranking today. They also have an event planned for Saturday in Calgary.

It was billed as an audio mob and had people listen to instructions while wearing something red, blue, yellow or green. There were even some parts that included blowing up balloons.

You may have heard of or seen Improv Everywhere's famous annual No Pants Subway Ride, which has happened this year on Jan. 10 in Calgary and dozens of cities around the world.

Charlie Todd of New York-based Improv Everywhere is the man behind the prank collective with the tagline, "We cause scenes."

"The goal is to create a unique and unusual experience for the random strangers who witness it, hopefully giving them a laugh and a smile and a great story to tell," says Todd.

Today's participatory prank is no different. Called the Mp3 Experiment, it has been successfully done in Berlin, Adelaide, Australia and on several college campuses in the U.S.

Those who participated in today's event had to download onto their mobile device an original Mp3 file, which is about 45 minutes long. Then synchronize your watch to an atomic clock on the website.

"It's nothing but pure joy," said Todd. 

Check out the High Performance Rodeo website for details on Saturday's events by clicking on the calendar date Jan. 15, or visit the Improv Everywhere website and click on "Tour" for more details.

Check out what was happening today during the High Performance Rodeo and Improv Everywhere event today: