Movie star Colin Farrell has confirmed he'll be among the stars acting out scenes tragic Heath Ledger never got to shoot in his final film, confessing it'll be an "incredibly painful tribute."

The Irish actor, Jude Law and Johnny Depp will help director Terry Gilliam complete the film he started with the late Ledger.

The superstar trio will pick up the role Ledger was playing in "The Imaginarium of Dr. Parnassus" before he accidentally overdosed on prescription drugs last month.

And Farrell admits he was flattered to be asked to help Gilliam complete Ledger's last film.

He tells the Sydney Daily Telegraph newspaper, "I will be honored to be part of that.

"It makes me feel uncomfortable to think about it too much and to get into it really here, but it's an incredibly painful honor... and an honor I wish wasn't bestowed (on me), but an honor none-the-less.

"It's about getting Heath's work out there... He's too good for any of his work not to be seen, you know, and I'm really keen and looking forward to doing it and just doing the best job I can do."

The film, about a magical traveling theatre, also features movie veteran Christopher Plummer. Production on the London set has been suspended since just before Ledger's death.