Change is afoot at Mono, the Minneapolis ad agency that in the past seven years has moved from a glorified south Minneapolis garage to a 10th-floor Uptown penthouse with a panoramic view of the city.

The agency's staffing is approaching 100, up 40 in the past 18 months. Gross billings last year were $108 million, more than double the level from four years ago.

A slew of new clients dot the agency's roster, including legendary shoemaker Sperry, the fast-growing restaurant chain Smashburger, the USA TV network, the sport drink Propel and Children's Hospitals and Clinics of Minnesota.

There are even plans for office expansion into new geographic markets.

With that amount of change, agency founders Jim Scott, Michael Hart and Chris Lange have had to manage growth in a measured way.

"It's about vulnerability," Hart said. "You have to be open to criticism. You have to be open to your idea not being chosen, and that is hard to do in a business that runs on ideas."

New hires at Mono are subjected to "onboarding" — a "Mono 101" course to introduce them to the agency's philosophy.

"It's about keeping our values and everyone's focus to maintain a culture of creativity and innovation," Scott said. "We have the 're-'s.' Re-think, re-imagine and re-invent. It's a phenomenal time to be doing what we do. People see brands in a different, more rich, way."

In advertising, creativity is king, ideas are currency and client whims represent the wild card, which mono was harshly reminded of earlier this year when one of its major clients substantially reduced its work with the agency.

"Within 20 minutes, we gathered all of our people together and told them what we knew and what we didn't know. We could have sat back and not told them anything but we wanted them to know what we were working on," Scott said.

Scott wouldn't identify the client.

"We've already replaced that business and continue to grow," Scott said, noting there were no layoffs associated with the business loss. "We were hiring during that time."

The loss of that major client allowed Mono to diversify its portfolio so it wasn't too reliant on a few accounts. It also opened up new creative opportunities for the staff.

"We want people to come here and do the best work of their careers," said Scott.

Mono thrives on big ideas. Back in 2005, it came up with the phrase "Characters welcome" as a tagline for the USA Network. In 2008, Mono did the launch for an AMC pilot of an edgy experimental series called "Breaking Bad." A few years later, the agency came up with the phrase "Lean forward" as the signature for MSNBC.

Mono's next big campaign is for Boston-based Sperry, a staple in the boat-shoe world since 1935.

The agency's assignment is to stretch the appeal of Sperry's Topsider brand and other brands from its old preppy New England base to the world of millennials by stressing spontaneity, adventure and purpose, traits associated with that demographic.

"You've got to get to that younger audience," Scott said. "It's a huge cultural shift."

Two teams of Mono workers are assigned to the Sperry account.

The advertising work features pictures of people at play with taglines such as "The best stories are written with our feet" and "If the earth has an edge, find it."

But the capstone to the campaign is a Sperry-paid adventure for 80 social media-adept consumers to travel to all corners of the world and bring back stories to post on in the Internet. It is known as the "Odyssey Project" and commemorates the company's 80th anniversary.

Three early participants included relatively well-known New York portrait photographer Andre Wagner and two members from the Swedish rock band Shout Out Louds.

Their stories and those of others are posted on Sperry's website,

Mono continues to operate in a financial partnership with MDC Partners, an advertising holding company that owns 49 percent of the agency.

"The relationship is still working great," Scott said. "With that comes the opportunity to do other things like open another office. It gives us the wherewithal to do that."