MIAMI — In a new television ad, Sean "Diddy" Combs, seeking a late-night snack, visits the mansion of Burger King's chief executive. The CEO — an actor, not current chief executive John Chidsey — takes the hip-hop mogul and his entourage to a Burger King and opens it, just to satisfy their appetite.

In real life, keeping restaurants open after midnight is just one of many changes the world's No. 2 hamburger chain recently made that have helped the brand overcome years of weak management, sluggish sales and disgruntled franchisees.

"We've cleaned up a lot of issues and really built ourselves a very solid foundation from which it is much easier to grow," Chidsey said.

Burger King went public in May 2006 and has seen its stock double since August. It has reported 13 consecutive quarters of positive comparable sales growth and initiated a worldwide expansion strategy, with a goal of opening about 200 new restaurants this year. Average restaurant sales of $1.17 million for a 12-month period ending March 31 are an all-time high. The stock price has doubled to about $26 after bottoming out at $12.41 last August.

Success has come from new "premium" flame-broiled products with high profit margins, quality chicken products and value menus; and a marketing campaign that brought back the King and the "Have it Your Way" mantra and also used Spider-Man and SpongeBob Square-pants.

The turnaround dates to when Texas Pacific Group, Bain Capital and Goldman Sachs Capital Partners bought Burger King from Diageo PLC in 2002, and continued when the management team led by former CEO Greg Brenneman took over in 2004. Before then, profit margins had slipped behind fast-food industry leader McDonald's Corp. and No. 3 burger chain Wendy's International Inc.

"Burger King, because it had had so many management teams, it had had so many advertising agencies, so many different strategies, I think the consumer was very confused," Chidsey said. "So bringing back the King, bringing "Have it Your Way" back, lots of things like have certainly helped people talk about the brand again."

Chidsey, who joined Burger King in March 2004, says management stability is a positive, especially in relationships with franchisees. More than 90 percent of Burger King's roughly 11,200 restaurants are owned by franchisees, who at one point saw sales decrease for six straight years.

Meanwhile, new stores are smaller, reducing building costs by 20 to 25 percent, Chidsey said. They sit on a half-acre of land rather than a full acre, and have 40 or 60 seats compared with 100 or more — following studies that show only about 20 percent of customers eat inside.

Burger King is aggressively going after markets abroad, where there is room for growth. Burger King opened new stores this month in Japan and Nanjing, China, while announcing development agreements in Egypt and Poland.

While most of the picture seems healthy, Burger King faces criticism that it's lagging behind in cutting trans fats. The Center for Science in the Public Interest sued the company in May, claiming it had failed to set a definite timetable for the change.

Burger King says it may complete a rollout of trans-fat-free oil in the United States and Canada by year's end, based on the success of one blend it is testing. But the change will be delayed until 2008.