THE ESSENCE: Growth hasn’t stymied TBWA’s creativity or agility. The U.S. agency now has $2.4 billion in billings, with clients ranging from Nissan North America to Apple to Mars. It’s also picked up work from McDonald’s, Pepsi-Cola Co., and snatched the $330 million Visa International account from Omnicom Group sibling BBDO. The shop has created integrated services, including direct response shop Tequila and interactive shop agency.com. The agency is also formalizing Jean Marie Dru’s disruption concept.