Nat 'King' Cole had a nightly singing engagement at a Lake Tahoe nightclub. He would commute daily between Lake Tahoe and the set in order to do both. Everyone noticed that Cole was coughing a great deal whenever he was on the set and losing weight, but most figured he was just running himself down with such a gruelling schedule. Unbeknownst to them and to Cole himself, he was already very sick with lung cancer.
At his acceptance of the Oscar, Lee Marvin opened by saying, "Half of this probably belongs to a horse out in the Valley somewhere".
Lee Marvin earned just $30,000 for his work here. Following his Oscar win, he was earning up to $1,000,000 for Paint Your Wagon (1969) and Monte Walsh (1970).
Lee Marvin's larger-than-life personality and fondness for tipping back the bottle made the actor a raucous but irresistible presence on the set. "Working with Lee Marvin was an unbelievable experience," said Dwayne Hickman. "Never have I met such an outrageous personality. Lee loved to drink, and the more he drank, the more outrageous he became. He had a story about everything and everybody. He also had very definite theories on acting and a style that was all his own. Lee figured if a little bit was good, a lot would be so much better. As a result, each take of a scene was bigger than the last." According to Hickman, Marvin sometimes used alcohol to enhance his performance as the drunken Kid Shelleen. For instance, the very first scene that Marvin shot was the one in which everyone meets Kid Shelleen for the first time, and he is falling down drunk. "He rehearsed several times," said Hickman, "and then went behind the barn and took a shot of vodka to steel himself. I ran into him in front of his dressing room where he had just gotten sick. When I asked if he was all right, he said, in typical Lee Marvin fashion, 'Tension, baby...just a little tension.'"