Colin Jude and Johnny Honor Heath

Colin Farrell, Jude Law, and Johnny Depp -- the three actors who stepped in to help complete Heath Ledger's final film, The Imaginarium of Doctor Parnassus -- are speaking out and paying tribute to the late actor.

Ledger (pictured), who was nominated for his first Oscar for playing gay in Brokeback Mountain and won the Oscar posthumously this past year for his work as the Joker in The Dark Knight, died nearly two years ago while still shooting the Terry Gilliam-directed Parnassus.

"Three of us had been asked to complete a task that had been set in motion by a man we greatly liked and respected as both a person and an artist," Farrell said on Ledger. "Being part of this film was never about filling Heath's shoes as much as seeing them across the finish line. How I wish he had brought the film to its completion himself."

Law said stepping in to help finish the film "was a tribute I felt compelled to make," while Depp credited Ledger with being "the only player out there breathing heavy down the back of every established actor's neck with a thundering and ungovernable talent."

The Imaginarium of Doctor Parnassus opens in select theaters Christmas Day.