what's the theory behind the kokomo chord progression, esspecially when it switches from F major to F minor... the chord progression is below.

C Cmaj7 Gm7 F Fm C Dm G

And also, in the "fun, fun, fun" intro, what scale are they using? i'd guess it's a Eb Minor Pentatonic with an added major third. The song is in Eb i figure since the main progression is Eb Ab Eb Bb...

Anyways, any insight into why this works theoretically would be appreciated.