Maria Sharapova was inducted into the International Tennis Hall of Fame on Saturday evening, and Serena Williams made a surprise appearance to introduce her.

Serena Williams and Maria Sharapova were rivals during their tennis careers, but they are now friends in retirement.

Hall of Famers Martina Navratilova, Jim Courier, Stan Smith and Andy Roddick were among those in the crowd, wearing their blue Hall of Fame blazers. Sharapova and the Bryan brothers also received a cast tennis racket that is the hall’s newest offering to inductees.