I waited years for a decent adaptation of Dostoyevsky's The Double - then two come along at once! A sincere but naive young man works in a backbreaking and thankless role - managing a cabaret show. Every decision he takes seems to backfire, and just when things can't get any worse a mysterious stranger appears, almost identical to the hero yet effortlessly popular and successful, and worse - nobody else notices the difference.
The cause of the splintering becomes clear: Kermit's longstanding internal conflict over his feelings for Miss Piggy. Now his ego is banished to a metaphorical Siberian prison while his id, in the form of Constantine, runs the show in more ways than one. However a series of subtle cinematic devices serve to indicate that they are two sides of the same frog - the beauty spot that supposedly distinguishes them but can appear or disappear too easily, or the beautifully filmed scene where the two characters see each other through a mirror.
Admittedly it's a loose adaptation but I think Dostoyevsky would be proud to think that his work had inspired this intelligent and challenging film.