Billy Crystal's impersonation of Muhammad Ali is considered legendary for its accuracy and affection, a routine that the boxing champion himself loved and which launched a lifelong friendship between the two. Crystal's spot-on impression was so beloved that Ali personally selected him to deliver a eulogy at his 2016 memorial service, where he again used the impression to honor his friend. Credit: Greg Garrison Productions | History In Pictures

Comedian Billy Crystal shares a story about doing an Ali-Cossell impersonation for his close friend, Muhammad Ali, during a memorial service for the champ. More: http://nbcnews.to/1szk0MG | NBC News

The great Billy Crystal returns to The Late Show and shares some of his trademark impressions, including a spot-on Bob Woodward. Stick around for more with Billy Crystal and check him out on Broadway starring in, “Mr. Saturday Night,” now playing. | The Late Show with Stephen Colbert