There is a blurb about Willie Nelson at Slate: In the article, the writer says that Willie Nelson is a master of all songs, proved by his version of "Rainbow Connection:
"a ridiculous piece of doggerel originally performed by Kermit the Frog, which Nelson turns into a ballad for the ages. Like just a few other master vocal stylists—Charles, Sinatra, Billie Holiday—Nelson is capable of redeeming the worst schlock, locating the kernel of real feeling in the most absurd material. Listen to him lagging teasingly behind the beat in 'Rainbow Connection,' and to the truly lovely succession of notes he hits singing the lines, "I know they're wrong, wait and see."
It is true that his version is lovely, but I don't know how you can call that song doggerel. First of all, the version sung by Kermit the Frog is just as well done as Nelson's. Second, when Kermit sang it, he did it in a movie made for children, and I don't know a single person who saw it as a child who doesn't love that song. Just because a kids' movie appeals to adults doesn't mean it was intended for them. So there! On a somewhat-related note, I saw Jon Stewart interview Kermit a while back, and Kermit just destroyed him (in a good way). Also, I think the Muppets might be Advanced.