Billy Crystal stopped by The Tonight Show on Thursday, where he and Jimmy Fallon remembered Robin Williams with several thoughtful, funny stories. Jimmy acknowledged Billy's special tribute to Robin Williams at this year's Emmys, and Billy said, "I really was worried I was not going to get through it." The comedian went on to talk about some of his most memorable moments with Robin, saying of his longtime friend, "He had the biggest set of balls ever on a stage. He was fearless. That was what I loved about him so much, and his commitment to the comedy was stunning." Watch the full interview above to hear Billy and Jimmy's best Robin Williams stories, then check out some beautiful, insightful Robin Williams quotes to remember.