It was Serena Williams all right, but not as tennis fans know her. The 43-year-old appeared at Super Bowl LIX on Sunday as the Philadelphia Eagles beat the Kansas City Chiefs 40-22, but the iconic American wasn’t there purely as a fan.

Instead, she starred, briefly at least, in the iconic half-time show at the Caesar’s Superdome.

While American President Donald Trump was leaving the venue having decided he’d seen enough, Williams made a shock appearance on stage alongside rapper and headline act Kendrick Lamar.

As Lamar performed his Not Like Us tune in front of 65,719 people, the 23-time Grand Slam champion surprised the crowd by appearing alongside him. And it was anything but an unscripted act, with Williams doing a Crip Walk dance while gazing at the cameras.

It wasn’t the sort of behaviour that would have been tolerated by the All England Tennis Club, whose emphasis on tradition and etiquette contrasts vastly to America’s showpiece sporting event. And on social media, Williams herself acknowledged that notion.

"Oh, I did not Crip Walk like that at Wimbledon,” she filmed herself saying, while smiling broadly. “I would have been fiiinnneeed!"

Clearly enjoying herself, the former world No.1 finished off by pouting into the camera. And it wasn’t the only clip posted to her Instagram and X accounts after the Eagles sealed glory.

Other footage showed her backstage before heading out to the main stage, appearing focused as she went through her Crip Walk routine. She captioned it: “Let's go Super Bowl halftime??! I died a little!"

There was also a video of Williams receiving her make-up while in the dressing room area. “A little behind the scenes,” she wrote.

The appearance of the icon was timely, following calls from Novak Djokovic to make the sport more entertaining to fans. The Serbian wants tennis to use set breaks to resemble the acts seen at the NFL's Super Bowl and the NBA.

It wasn’t just sporting stars on show in Louisiana though. Actor Samuel L Jackson, dressed as Uncle Sam, also played a cameo role on the stage as did R&B singer SZA.