A simple smile can be infectious. That’s the idea behind "Smile Back," the latest installment in Coke’s "Where Will Happiness Strike Next?" global film series.

The brand dispatched a team of "Smile Starters" around the world in search of yes, you guessed it, smiles. The friendly ambassadors sporting red t-shirts and riding red bicycles approached strangers in different locations – from Canada, to Pakistan, to Tunisia – and simply smiled or attempted to break the ice with a silly, grin-inducing gesture. Those who returned the gesture were rewarded with an ice-cold Coca-Cola or other fun prizes, including sunglasses, hats and the “Smile Cycles” themselves. The experiment was designed to use the contagious power of a smile to create a chain reaction. A smile movement, if you will.

The end result is “Smile Back,” a short film concepted, produced and crowdsourced in partnership with Coca-Cola teams from six countries, plus Victors & Spoils and MOFILM. Watch it below, and read the "Smile Backstory" for more on how this unique, fully crowdsourced project came together.

Read Fast Company's coverage of the film.