Billy Crystal reminisces about Rob Reiner as he reflects on their time in When Harry Met Sally.

On Tuesday, April 14, Crystal appeared on The Late Show with Stephen Colbert, where he discussed Reiner’s directing him in both 1987's The Princess Bride and 1989's When Harry Met Sally.

Crystal recalled meeting Reiner while guest-starring on All in the Family in 1975, calling it “a good year” for him.

Their friendship grew off-screen, with Crystal describing Reiner as “hilarious, devoted, opinionated, in the best way,” adding they spoke about everything and that Reiner became “an uncle” to his children.

He said their habit of calling each other over in everyday moments later inspired the iconic phone call scene in When Harry Met Sally.

“He was going through a tough divorce from Penny Marshall at the time, and we were on the phone constantly,” Crystal remembers. “And there were moments of, we'd be watching a movie together, like Casablanca, and we would do that and go back and forth.”

In When Harry Met Sally, the central characters retreat to separate bedrooms, each watching Casablanca on television while continuing their ongoing argument over the film’s meaning.

“We were watching, remember arena football?” Crystal said. “We were going back and forth, and we said, ‘What about arena yachting? Maybe there's Arena Yachts.' ”

Rob Reiner and his wife, Michele Singer Reiner, died at their Brentwood home in Los Angeles on December 14, aged 78 and 70, respectively.