Diet Pepsi's latest celebrity campaign, with Josh Duhamel as an irresponsible grocery employee, earned the top spot in the world of viral video. In the ad, Mr. Duhamel is halfheartedly undercover as he operates the grocery check-out line; sometimes he poses with fans, and sometimes he shrugs as shoppers say, "you should be an actor!" His antics, which include throwing customers' produce across the store and grocery cart-racing, racked up 2.3 million views with an effort from Weber Shandwick, with director P.R. Brown and Bau-Da Design.

It has become part of Pepsi's trademark strategy to capture consumer attention through celebrity videos. Recent Diet Pepsi spots included Sofia Vergara and David Beckham. In a similar vein, PepsiMAX's strategy is to take sports celebrities such as Jeff Gordon and Kyrie Irving deep undercover and shock the people they come across. In Mr. Irving's spot "Uncle Drew" last year, Pepsi MAX dressed the NBA star to look like a tubby, 60-year-old geezer who then shocked 20-somethings in a neighborhood basketball court by out-performing them.