I would find it so funny if they used the princess frog story- because of the Kermit song. and somehow made it so that WWwas turned green because she kissed a magic frog or something, or perhabs she is the frog turned human 🙂
But Ialso like the idea of Regina giving her a poisonous apple turning her green.
The Kermit song is about accepting yourself whatever color/person you are. Do the WW not accept herself for what she is? She blames some of the characters we know for what she’s become- green, thats why she wants revenge..