And What's Wrong with That?

And this morning we have Silly Love Songs! But the earworm is a tricksy thing. It keeps alternating between the Wings version and the version covered in Moulin Rouge. Ah, Ewan... Anyway, Paul McCartney "can't explain, the feeling's plain..." yada yada yada. But can anyone, ANYONE, explain this to me? Like any part of it at all? If you can, you win.