The list author says: "Jack Lemmon and Walter Matthau were two actors that when paired together for a comedy film, it was always a success. These two had their own solo careers and movies of their own that were highly acclaimed, but the film Neil Simon's The Odd Couple (1968) is the most enjoyed and remembered of the two togther. They have appeared in 9 movies together. In their senior years, they paired again for Grumpy Old Men (1993), Grumpier Old Men (1995). Followed by The Odd Couple II (1998), their last film together. Walter Matthau died July 1, 2000 of heart attack at 79. He had colon cancer that spread to his lungs, liver and brain. Jack Lemmon died June 27, 2001 of colon cancer and bladder cancer at 76. They are buried next to each other."
"The Fortune Cookie (1966). Walter Matthau used to joke that he met Jack Lemmon in a Jewish Deli. Walter had a heart attack during production. He lost 35 pounds. 5 months later they continued filming with Walter in an overcoat."