A month after leaving the agency where he spent more than a decade, Crispin Porter & Bogusky chief creative Rob Reilly has resurfaced at McCann, where he will become global creative chairman in March. The move to McCann is a homecoming of sorts for Mr. Reilly, who was a junior copywriter at the agency in the mid '90s working on Coca-Cola account.

The move coincides with a reshuffling of the creative ranks at the IPG agency. Linus Karlsson, who was chief creative officer of global brands at McCann Erickson, moves to creative chairman of Commonwealth, while Andreas Dahlqvist, who was deputy chief creative officer of global brands, becomes chief creative officer at Commonwealth and president of the McCann Creative Leadership Council. Commonwealth is McCann's dedicated agency for General Motors' Chevrolet account. The McCann Creative Leadership Council is an internal group responsible for inspiring creative excellence throughout the McCann Worldgroup network.

Mr. Karlsson will also be forming, with the blessings of IPG and McCann Chairman-CEO Harris Diamond a new venture, but details will not be released until the spring.

While the reshuffling was underway before Mr. Reilly was hired, Mr. Karlsson said that his arrival "opened up opportunities" for McCann to improve its talent and its structure. "We do need every single smart, talented creative leader we can get," he said. "McCann is big enough to have a great collective of strong leaders." In fact, it was Mr. Karlsson who initiated contact with Mr. Reilly, sending him a note asking him to talk after news broke of his leaving Crispin. According to Mr. Reilly, one beer was all it took to get them to ask why they weren't working together.

McCann's Mr. Diamond said that "the only thing people buy from us is our creative skillset coupled with our understanding of brand, so anything we can do to build that is a good thing." What he liked about Mr. Reilly, other than his creative talent, was his sense of humor and "his focus," he said.

Mr. Reilly joined Crispin as copywriter in 2003, later serving as the global creative director on Burger King. He was named worldwide chief creative officer in 2010. Crispin is not replacing Mr. Reilly. Instead, it is restructuring the creative department where executive creative directors in individual offices will have more autonomy, a structure developed by Mr. Reilly, CEO Andrew Keller, and Chairman Chuck Porter.

Aside from Burger King, Mr. Reilly helmed creative on accounts like Microsoft, Dominos, Old Navy and Kraft, and helped propel the agency to dizzying creative heights, including winning awards at Cannes and the One Show. In 2012, Ad Age's sibling site, Creativity, named him the third-most-awarded creative director of the year.

"I love CPB, and I owe a lot to the people at CPB," Mr. Reilly told Ad Age. "At some point, you find yourself asking 'What's next' for myself and 'What's next' for Crispin?" he said.

McCann Worldgroup had a good year creatively, propelled by the Melbourne office's "Dumb Ways to Die," the public-service superhit for the Australian Metro. It also added new clients, including the consolidated global Chevrolet business, Zurich Insurance and SABIC globally. In the U.S., it now counts the USPS, Lockheed Martin and Jose Cuervo on its roster. Coming up is a "big quarter," for the agency according to Mr. Karlsson, with work for the Winter Olympics, the Super Bowl and the Oscars on its way.