Williams' surprise appearance to induct Sharapova was "months in the making" and required the code name of another female icon.

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.

Williams and Sharapova were not always on great terms, each admitted in their speeches, but came to share a mutual respect and a growing friendship since retiring.