Billy Crystal gave a wonderful tribute to Ali toward the end of the 3-hour memorial service. I can't find his tribute from today, but here's a tribute called "15 Rounds" that Crystal did on Ali's retirement in 1979:

https://vimeo.com/169300354

Found it: Here's a link to the memorial service tribute from Crystal later. It was very funny, and very moving. Take the time to watch this.

https://www.youtube.com/watch?v=Go2kSgiuR3c

Here's a tribute Crystal wrote for USA Today:

http://www.usatoday.com/story/sports/boxing/2016/06/04/muhammad-ali-billy-crystal-essay/85373424/