I suspect some of you even if you're not a musician were once shown how to play "Blue Moon" chords on a piano. That chord progression, also known as "We want Cantor", has been used in many other pop songs. The chord progression based on steps of a major scale are one, six, two, five, one or in the key of G: G Em Am D G or usually just the first four chords repeated but I've put the final G there for a reason.
Composers use composition devices to come up with new ideas. One of those is a "retrograde" which is usually a melody reversed or mirrored. This also can be done with chord progressions which is even more unusual. So if you reverse that "Blue Moon" chord progression you get: G D Am Em Start on the Am like this: Am Em G D and you get this: http://www.youtube.com/watch?v=WQvM4EM0lO8
