It's been done before

The Simpsons had a clip show many years ago that was framed by the family watching the 1969 hit Paint your Wagon. Naturally at the time I assumed that this was some clever joke by the writers, because it just seems so stupid to have Lee Marvin and Clint Eastwood in a musical, but when my dear old mother explained to my brother and I that this was in fact a real movie I was horrified. Then years later I wanted to see this cinematic monstrosity, and was even more disappointed to find that the songs weren't nearly as memorable as the ones in the Simpsons clip show.