Billy Crystal remembers Muhammad Ali with '15 Rounds'

Billy Crystal's '15 Rounds' of Muhammad Ali (10:55)

Go back to 1979, when Billy Crystal performed a one-man show representing 15 rounds in the life of Muhammad Ali. (10:55)

Muhammad Ali's death late Friday night sent shockwaves throughout not only the sports world, but also the entertainment world, with many notable figures taking to social media to pay their respects to the three-time heavyweight boxing champion and to share personal stories of what he meant to them.

On Friday afternoon, before Ali passed away, actor and comedian Billy Crystal tweeted a video of his 1979 performance at Ali's retirement ceremony, called "15 Rounds," with the caption, "For the greatest man I have ever known." The 11-minute performance is a mix of both reverence and humor which highlighted the legendary moments of the champion's storied career. Crystal and Ali became friends in 1974 when he made an appearance on a television special honoring Ali in which he imitated both the boxer and well-known sports personality Howard Cosell. Crystal wrote in USA Today Sports in 2010 that Ali loved it and from then on started calling him "little brother."

Ali's reaction to Crystal, which is viewable throughout the performance in the top-left corner of the video, shows that an athlete who was known for dishing out verbal jabs could laugh when someone playfully poked fun at him.