I reckon the 'Lupin loved Lily' ship ain't bad! 'Lupin bit Lily'... ?? I dunno. I don't think it explains the sorrowful and 'deep' look Lupn had in the move PoA.

What do you think was in the PoA movie that "foreshadowed" events in the nect books???

Knowing Jo, it could be anything from' Lupin loved Lily', to the 'Demeators attack Hogwarts and the House Elves save them all' !!. My money's still on the Lupin connection.