The induction ceremony on Saturday night at the International Tennis Hall of Fame featured identical twins and longtime rivals. Serena Williams surprised the gathering by stepping onstage to introduce Maria Sharapova, describing the honoree as a "former rival, former fan and forever friend." Their competition began when Sharapova beat Williams in the 2004 Wimbledon final, a match that made the 17-year-old a global star. They conceded in their speeches that their relationship has been tense in the past, the Boston Globe reports. But it's improved—especially since they retired—to the point that Sharapova asked Williams, who's not yet eligible for induction, to make the introduction to the 900 attendees in Newport, Rhode Island.