Not Ready for Prime Time.

Billy Crystal had a hard time keeping a straight face around his former “Saturday Night Live” co-star Christopher Guest.

During an Oct. 12 Q&A with Whoopi Goldberg at PaleyFest NY 2026, the comedian — who was an “SNL” cast member from 1984 to 1985 — revealed he “couldn’t even look at” Guest during sketches.

“I couldn’t look Chris Guest in the face,” Crystal, 78, said. “I did more sketches with Chris than anybody else. And we had a great group: Marty Short, Chris Guest, Julia Louis-Dreyfus, Rich Hall, but Chris and I … he’s so funny.”

Guest, also 78, was a cast member during Season 10 of “SNL,” notably appearing alongside Crystal in the sketch comedy show’s recurring “Willie and Frankie” sketches.

“We did these guys; they were masochists. They would hurt themselves, and we’d go, ‘I hate when that happens,’” Crystal recalled to Goldberg, 70. “Chris makes me laugh like crazy. There were so many times I couldn’t even look at him. I would just look the other way when he had lines to do.”

The “When Harry Met Sally…” actor went on to recall how Guest, who’s married to Jamie Lee Curtis, once “switched a line” during a “Willie and Frankie” sketch.

“He was supposed to say, ‘So I went home, and I took off my clothes, and I bathed in a vat of gin, and I rolled back and forth on some push pins,’” Crystal explained. “And I went, ‘Oh.’ And he goes, ‘Yeah, I hate when I do that.’”

But when it came time to perform the sketch live, Guest delivered the line a little differently.

“So now we’re on the air, and he goes, ‘So I stripped down to the nude,’ and I went, ‘Oh, you bastard,’” Crystal said. “It’s just a funny way of saying I got naked … and I just couldn’t control myself.”

Crystal also had high praise for Short, who was a cast member during Season 10 of “SNL,” and the late Robin Williams, who appeared on the show several times prior to his death in 2014.

“Marty [Short] is as funny as he gets,” he said. “I’ve been around amazing people, and we were blessed to be around one of the geniuses [who] I’ve ever been shoulder to shoulder with, and that was Robin [Williams].”

Beyond “SNL,” Crystal and Guest also worked together on other projects, including “This Is Spinal Tap” and “The Princess Bride,” both directed by the late Rob Reiner, who died alongside his wife, Michele Singer Reiner, in December 2025.

Most recently, Crystal opened up about his final conversation with Rob before the filmmaker was fatally stabbed at his Los Angeles home.

“We had spent the night before together and [were] talking about our careers together,” Crystal said during an April appearance on “The Late Show with Stephen Colbert.”

The pair, who had chatted at Conan O’Brien’s 2025 Christmas party, discussed how the movie business had “changed” over the years.

“We talked about the fact that you can’t control how a movie is going to do. What you can control is the experience of making it,” Crystal recalled. “And the experiences that we had together and that he had with his cast of his other movies was so extraordinary.”

“He said, ‘That’s something you’ll always have. Hits are great to have, but it’s the people that you hold on to,’” Crystal added. “And so I kept that in my heart.”