A morally ambiguous story, overview of Wondrium episode themes, and win a yearlong Wondrium subscription / a DVD set of my series on storytelling!
Frog 100%. I, too, was a frog-chaser as a kid. Need I say more?
It's striking how you highlight The Frog King story here. I frequently muse upon Bruno Bettelheim's take (remembered as "The Frog Prince"). Complementary and parallel to your moral interpretation, his classic - The Uses of Enchantment - approaches the story through a psychological - Freudian - filter. You each agree the princess has some growing up to do! The story in its ambiguity presents imagery and symbolism constructive for psycho-sexual integration. The princess cannot grow into her integrity as a fully mature, complete, adult woman until she accepts the frog (although she does so only in its guise as prince).
Plus, the duality in this one story parallels the duality you trace throughout your course!