For those of you not in the know, this was the movie that Heath Ledger was filming at the time of his demise. The film wasn't completed at the time, and so for certain portions, his character is played by one of three different actors, being Johnny Depp, Colin Farrell, and Jude Law. Of course, none of these men look anything like Ledger, although that's not really an issue given the nature of the film.
Dr Parnassus is a two thousand year old monk of sorts, with a gambling problem, and a long time gambling partner in the Devil. Throughout the ages the Devil has approached him, and made various wagers, which is where the good doctor's immortality came from. In the present, Parnassus wanders around performing shows with his daughter, played by Lilly Cole (a relatively new face, who has that same problem that Cristina Ricci does, her face makes her look more like a porcelain doll than a real person), a dwarf played by Vern Troyer, and some other guy who's in love with the daughter, and is ultimately forgettable.
Their apparent purpose is to travel around, and convince people to enter a fake carnival mirror which takes them to the Imaginarium, which in turn is actually the inside of the doctor's mind. Once in the Imaginarium, their imaginations become real, and they eventually make a choice between selfless enlightenment, or selfish greed. Typically the nature of the bets between Parnassus and the Devil revolve around who gets the most souls from this practice.
Ledger's character Tony is found by the trip, hanging by his neck under a bridge, and he miraculously survives because of a pipe whistle that he lodged in his throat. The stand-ins occur whenever Tony enters the Imaginarium, and thus takes on a different self image, because of his imagination.
Ultimately, I'm not sure that I liked the story of this movie, there were no real heroes, a lot of imperfect people, and one Devil. Regardless of how I felt about the story, visually the movie is very stunning, from the vagabond rags of the travelling troupe, to the Devil's black bowler, and of course, the acid trip worthy Imaginarium sequences, the movie always has a clear idea of what feeling each scene should have, and executes it with a style that I find impossible not to love.