With the insight that there is no minimum age to set up a LinkedIn account, Coupe Buenos Aires hit on an effective and dramatic way to highlight the scandal of child labor, with 215 million largely invisible underage workers around the world.

The Argentine agency invented companies in industries that often employ and exploit children (textiles, toys, coffee and food) and then created fake LinkedIn profiles in different countries for about 50 children who supposedly worked there. Those fictitious children then each issued hundreds of invitations to LinkedIn users to connect with them. Anyone who accepted their invitations was directed to the website thechildrennotwork.org, filled with detailed information about child labor.

"You can be 8 and have a LinkedIn profile," said Francisco "Coco" Olivera, Coupe's chief creative officer.

The client, an ad hoc group called Advertisers Without Borders, had "no budget, not even a peso," Mr. Olivera said. Using man hours and technology alone, the agency seeded The Children Notwork campaign on the network that is all about work, and watched it spread to other social media and get picked up by journalists and bloggers.

Coupe Buenos Aires was started in 2011 by Pablo Gil, a well-known creative who was Grey Group's Latin America creative director, along with Mr. Olivera, who worked with him at Grey, and two others, and has 25 staffers.

Where did the name Coupe come from?

"We're all from big agencies, and we wanted a more agile agency, like a coupe," Mr. Olivera said. "Big agencies are like trucks, and we wanted a car with high speed and few people."

In fact, one of the partners parked just such a car, a vintage Torino coupe made in Argentina, inside the agency during its first year. But Coupe Buenos Aires moved to new offices about a year ago, and the car doesn't fit into the lobby. Coupe Buenos Aires may not have a coupe any more, but Mr. Olivera, as a sideline, makes and sells retro bicycles.