In The Frog Prince (The Frog King) the role of the frog is slightly different. It is not only a messenger, it also wants to be a partner. Sharing food and drink and bed... Well, it can be easily interpreted as a tale about growing up, maturity and possibility of pregnancy. In older versions of this fairy tale this is even more obvious than in Grimm's.
Grimms changed the story into a moral about importance of a given word and keeping one's promises, but it is still mainly a story about responsibility which is - let-s face it - actually the favorite subject of brothers Grimm.
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