The film follows a travelling theatre troupe whose leader, having made a bet with the Devil, takes audience members through a magical mirror to explore their imaginations and present them with a choice between self-fulfilling enlightenment or gratifying ignorance.

[5] Ledger completed most of the movie's runtime, and then his role was recast with Depp, Law, and Farrell portraying transformations of his character as he travels through a dream world.

[7] An elderly sage, Doctor Parnassus, runs a travelling theatre troupe, which includes his teenage daughter Valentina, barker Anton, and dwarf Percy.

The troupe's main attraction is a portal to a magical "Imaginarium", a surreal dream world that transforms according to its participants' desires and offers them a choice between difficult self-fulfillment or easy ignorance.

Mr. Nick visits Parnassus and reveals that the rescued man is disgraced philanthropist Tony Shepard, who was hanged by Russian gangsters for owing them money.

Influenced by Valentina's desires, Tony's face changes to that of her dream lover, and they float along a river in a gondola, fulfilling their shared sexual feelings.

Mr. Nick frees Valentina's soul but does not reveal her location to Parnassus, who is abandoned to wander in despair, trapped in the Imaginarium.

Director Terry Gilliam and screenwriter Charles McKeown wrote the script,[9] their first collaboration since The Adventures of Baron Munchausen (1988).

"[11] Gilliam described the premise as a "fun and humorous story about the consequences of our personal choices in life",[12] and explained his goal for the film: "It's autobiographical.

I loved this idea of an ancient travelling show offering the kind of storytelling and wonder that we used to get, to people who are just into shoot-em-up action films.

[13] Gilliam repeatedly said in interviews that the character of Parnassus was meant autobiographically, a tale of an aging man with a vivid imagination in a world that does not listen anymore.

He was compelled to emphasise that upon the film's release many things might be mistaken as references to Ledger's fate but that the script wasn't changed apart from re-casting Tony with Depp, Farrell, and Law.

[21] The carnival scenes were shot at Potters Field between 10 and 11 December; shooting then moved to the abandoned Battersea Power Station for three days, where the production had set up offices nearby.

From 5 to 6 January,[24] the production filmed scenes with the Imaginarium at Leadenhall Market; shooting on this sequence managed an average of 70 set-ups a day.

[29] The imagery would have been similar to transformation techniques seen on Brad Pitt in The Curious Case of Benjamin Button and those employed on Roy Scheider's performance in his posthumous release Iron Cross.

"[30] Depp, a friend of Gilliam's who starred in Fear and Loathing in Las Vegas and the aborted 1998 production of The Man Who Killed Don Quixote, had been compared to Ledger by cinematographer Nicola Pecorini.

[25][39] After arriving in Vancouver on 26 February,[38] Colin Farrell joined the cast and began practicing scenes with them for several weeks while Christopher Plummer's bluescreen and interior work was done, only beginning filming proper on 10 March.

[24] This conversation proved to be the last sequence shot for the film, and involved a set completely improvised, on the day, to look like the ground at Battersea;[26] they did not have the budget for anything better, but the production crew came away quite impressed at how well it worked.

Wonderfully enchanting and beautiful, The Imaginarium of Doctor Parnassus is a uniquely ingenious, captivating creation; by turns wild, thrilling and hilarious in all its crazed, dilapidated majesty.

He was the only player out there breathing heavy down the back of every established actor's neck with a thundering and ungovernable talent that came up on you quick, hissing rather mischievously with that cheeky grin, "hey ... get on out of my way, boys, I'm coming through ..." and does he ever!!!

Heath is a marvel, Christopher Plummer beyond anything he's ever done, Waits as the Devil is a God, Lily Cole and Andrew Garfield, the very foundation, are spectacular, Verne Troyer simply kicks ass and as for my other cohorts, Colin Farrell and Jude Law, they most certainly did Master Ledger very proud, I salute them.

Though the circumstances of my involvement are extremely heart-rending and unbelievably sad, I feel privileged to have been asked aboard to stand in on behalf of dear Heath.

"[14] Gilliam finished editing the film by November 2008, and then work began on creating 647 computer generated imagery effects shots.

According to Designing the Imaginarium published by CBSnews.com, the scene with Doctor Parnassus's attempted suicide related to the style of Odd Nerdrum,[48] the Ladder World with Jude Law featuring "rolling hills with simple trees" was inspired by the art of Grant Wood,[49] the kitsch landscape from the beginning of the sequence with Colin Farrell took inspiration from Maxfield Parrish,[50] and Jose Maria Sert's mural of the Crucifixion in Rockefeller Center inspired the scene including the final minutes of Farrell's appearance in the film.

"[55] According to Gilliam, actor Colin Farrell also went on record for saying that he hadn't been simply playing the character of Tony, but that he was rather feeling like "channeling Heath".

[56] Gilliam also positively recalled people's commitment to Ledger's memory: "Everyone in the cast and everyone in the crew was determined that this film would be finished and everybody worked longer, harder and somehow we got through.

"[14] The film opens with St Paul's Cathedral in the background (by the north bank of the Thames), and the first show is performed under the rail tracks at Green Dragon Court, directly next to Borough Market, with Southwark Cathedral in the background (in Borough, London, on the south bank of the Thames), where the drunken lout molests the performers and then enters the mirror.

Tony is found hanging under Blackfriars Bridge, and the very large disused building in which the following scene (and several later ones) occurs is the interior of Battersea power station, farther west along the south bank of the river.

Supplementary material includes an audio commentary and an introduction by Gilliam, deleted scenes, wardrobe test for Heath Ledger, visual FX feature, and three featurettes titled "Behind the Mirror", "Building the Temple", and "UK Premiere".

The website's critical consensus is that "Terry Gilliam remains as indulgent as ever, but The Imaginarium of Doctor Parnassus represents a return to the intoxicatingly imaginative, darkly beautiful power of his earlier work, with fine performances to match all the visual spectacle.