In 1967, Clint Eastwood's career took off overnight with American theatrical releases of A Fistful of Dollars, "For a Few Dollars More" and "The Good, the Bad and the Ugly." Directed by the brilliant Sergio Leone, this trilogy of fresh-faced spaghetti westerns transforms Eastwood from TV cowboy (as Rowdy Yates on CBS's "Rawhide.") of a gun-toting antihero. The genre was reborn, and Eastwood suddenly became John Wayne for the Baby Boomer generation. He broadened his range and strengthened his popularity the following year by genre-hopping from the western "Hang 'Em High" to the cop "Coogan's Bluff" to the World War II spy thriller "Where Eagles Dare." By the time 1969 rolled around, he could do just about anything—and he did the unexpected.

Although musicals and traditional Westerns were declining in popularity, Paramount felt it could give both a jolt by staging a big-screen adaptation of Alan J. Lerner and Frederick Lowe's popular 1951 musical Paint Your Wagon. It's a rollicking show set during the California Gold Rush filled with memorable tunes and colorful characters. With veteran music director Joshua Logan ("South Pacific" and "Camelot") at the helm, it seemed like a safe bet to at least break even commercially; at most, it could turn out to be a box office setter and a top Oscar contender.

Casting would be key, and this is where Logan turned a safe bet into an odd gamble. Instead of looking for musically inclined actors to play the lead roles, he went with non-singers like Clint Eastwood, Jean Seberg and Lee Marvin. The result wasn't a disaster per se, but Eastwood still regretted it.

In an interview with Empire in 2017Eastwood thinks that perhaps the great new-found confidence is why he decided to star as the gold-digging Pardner opposite Lee Marvin's hell-bent Ben Ramson. I was crazy enough to try anything," Eastwood said. "I have always been interested in music, my father was a singer and I had some knowledge about it. Although what I was doing in that picture was not singing."

Technically, it was. Aesthetically, it was not very pleasing. While Logan's leads couldn't quite carry a tune (Marvin is much worse), Jean Seberg was voiced by veteran Anita Gordon to keep moviegoers from having their ears bleed.

Eastwood could see trouble coming and tried to leave the production before filming began, but Lerner and Logan flew to the set of Where Eagles Dare to convince him to stay. Eastwood relented, but continued to hide this decision. "Paint Your Wagon" took six months to shoot, an eternity an efficient actor-director known for bringing in films ahead of schedule and under budget. Although "Paint Your Wagon" eventually found an audience, it is still remembered as the odd duck of a movie musical.