Serena Williams and Maria Sharapova surprised tennis fans on Saturday when Williams walked out to introduce Sharapova into the International Tennis Hall of Fame. The two tennis stars shared a long rivalry that Williams described Saturday as “so electric and so iconic.

When Sharapova was inducted into the Tennis Hall of Fame on Saturday night, her former on-court antagonist provided the introduction. For many tennis watchers, Williams’s top secret cameo was shocking,

Sharapova was honored with an official U.S. Open ring Sunday at Arthur Ashe Stadium, following her induction into the International Tennis Hall of Fame. She accepted her latest hardware in the latest rendition of the tennis dress that changed the sport. “New York City, what a special place and special court,” Sharapova said.