The pair were set to play brother and sister in the 1993 romantic comedy, but they both quit, leaving the roles to ultimately be played by Aidan Quinn and Mary Stuart Masterson. The movie also co-starred Julianne Moore and Johnny Depp as the title characters' love interests.
Asked about the missed opportunity to work together in the past during a round-table interview with reporters in New York Sunday, Harrelson turned to Dern and -- pouring her a cup of tea -- said, "Once I knew you weren't in [Benny & Joon,] that was that."
The pair said they collaborated on a play in Los Angeles not long after the Benny & Joon saga, but had always hoped they would some day share the screen and were happy when Wilson allowed them to do just that.
"If we had just met it would have been a much different thing," Harrelson emphasized about the intensity of their Wilson characters' romance. "I just loved every minute of working with this lady here. I think she is one of the great actresses that we have. I was very, very lucky."
"Woody is the bravest, most beautifully open actor I could have ever dreamed up," Dern returned the compliment. "He's in my dream of... You know, if I got to be Ginger Rogers, who my Fred Astaire would be. But, beyond all of that, the physical comedy is mind-blowing and the fact that we both got to play out these very physical characters and how they use their bodies and to find the humanity within that, not just the joke. That is like the most delicious gift ever."
Co-starring Judy Greer and Cheryl Hines, Wilson opens in U.S. theaters on Friday. The comedy follows a lonely, brutally honest man as he tries to re-connect with his ex-wife and the young-adult daughter he never knew he had.