Crystal -- who was a longtime friend of the late comedian and, along with Whoopi Goldberg, a Comic Relief partner-in-crime -- told stories of playing baseball and cracking jokes with Williams.
But it was when he got serious, at the thought of having to refer to Williams in the past tense, that Crystal really put the loss into perspective.
"It's very hard to talk about him in the past, because he was so present in all of our lives," he said. "For almost 40 years, he was the brightest star in a comedy galaxy. While some of the brightest of our celestial bodies are actually extinct now, their energy long since cooled, but miraculously, since they float in the heavens so far from us now, their beautiful light will continue to shine on us forever. And the glow will be so bright, it will make your eyes glisten, and you'll think to yourself: 'Robin Williams, what a concept.'"
The fitting tribute was followed by clips of Williams from his stand-up and talk-show appearances. To finish, Williams was shown walking off stage in a single spotlight.