The Imaginarium of Doctor Parnassus is an upcoming fantasy film directed by Terry Gilliam and written by Gilliam and Charles McKeown. In the film, the leader of a travelling theatre troupe, through a deal with the Devil, takes audience members through a magical mirror to explore their imaginations. Christopher Plummer, Tom Waits, and Heath Ledger star in the film, though Ledger's death midway through filming caused production to be temporarily suspended. Ledger's role was recast with Johnny Depp, Jude Law, and Colin Farrell portraying transformations of Ledger's character Tony as he travels through a dream world. The projected release date for this film is 2009.

In the present day, immortal 1,000-year-old Doctor Parnassus (Plummer) leads a traveling theater troupe that offers audience members a chance to go beyond reality through a magical mirror in his possession. Members of the troupe include a sleight of hand expert, Anton (Andrew Garfield), and a dwarf, Percy (Verne Troyer), Parnassus had been able to guide the imagination of others through a deal with the Devil (Waits), who now comes to collect on the arrangement, targeting the doctor's daughter (Lily Cole). The troupe, which is joined by a mysterious outsider named Tony (portrayed by Ledger, Depp, Law, and Farrell), embark through parallel worlds to rescue the girl.

Director Terry Gilliam and screenwriter Charles McKeown wrote the script for The Imaginarium of Doctor Parnassus, their first collaboration since The Adventures of Baron Munchausen (1988). Gilliam described the premise as a "fun and humorous story about the consequences of our personal choices in life", and explained his goal for the film: "It's autobiographical. I'm trying to bring a bit of fantasticality to London, an antidote to modern lives. I loved this idea of an ancient traveling show offering the kind of storytelling and wonder that we used to get, to people who are just into shoot-em-up action films." The film received a budget of $30 million, considered unusually high for an independent production. Production began in December 2007 in London, at landmarks such as Battersea Power Station, Tower Bridge, and St. Paul's Cathedral. Production for the remainder was planned to be done in Vancouver.

On 22 January 2008, production of the film was disrupted following the death of Heath Ledger in New York City. Ledger's involvement had been a "key factor" in the film's financing. Although production was suspended indefinitely by January 24, according to Christopher Plummer, who plays Doctor Parnassus, Gilliam, determined to "salvage" the film, initially considered using computer-generated imagery to make Heath Ledger's character magically change his appearance, perhaps into another character, in order to keep his final work in the film, and, if the film were made, would dedicate it to Ledger. Actors Johnny Depp, Colin Farrell and Jude Law were cast to replace Heath Ledger, portraying transformed versions of Ledger's character while traveling through a magical realm. With the role recast, filming resumed in Vancouver in March 2008. Actors Depp, Farrell, and Law opted to redirect their wages for the role to Ledger's young daughter, Matilda, who had been left out of an old version of Ledger's will.