The Departed, on top of being riveting entertainment and superlative filmmaking, offers an excellent opportunity to look at the casting process and how the right actors can really help to get across the ideas of the movie. Each actor brings a wealth of associations with them to help raise the tension of the narrative and the expectations of the audience.
MATT DAMON, we know, was already a genius Boston guy in Good Will Hunting, so we not only buy his accent, but we know he's really smart. Plus, he played both Jason Bourne and Tom Ripley so we know he's good at lying to people and can kill with a cold heart.
LEONARDO DiCAPRIO we know was in Catch Me if You Can so we know he's good at fooling people, and he was in Gangs of New York so we know he can take care of himself in gangland, and he was in Titanic so we know that he's operating under a terrible burden of guilt and shame. Kidding. Sort of. But you know, ever since then he's kept scrunching up his brow and looking really pissed off, never more so than here, where regret and anxiety waft off of him in waves.
JACK NICHOLSON is more sui generis. He carries so much baggage with him that he presents a case all by himself. No one comes within striking distance of Nicholson's work in Hollywood today, especially since Brando died. He shows up and you pay attention. From Jake Gittes to Randall McMurphy to Jack Torrance to The Joker, he's a steamroller of associations and innuendo.
MARK WAHLBERG we know is tough from The Perfect Storm and Three Kings, but we know he's vulnerable too from those same roles. So we know he can hold his own against the stars in the short run, but we don't know if he can go the distance.
MARTIN SHEEN we know is tough because he killed Marlon Brando, but he was also President Bartlett so we know he's wise and fair. (This part, I've heard, was originally supposed to go to DeNiro, which would have lent a lot more surprise and tension to those scenes. Martin Sheen killed Marlon Brando, but he kvetched a lot about it beforehand and he struck him from behind when it came down to it. DeNiro would take your head off like swatting a fly and not even stick around long enough to watch your corpse drop to the ground.)
RAY WINSTONE we saw stand up to Ben Kingsley in Sexy Beast, so we know he's tough (they put a scar on his face for extra toughness), but we also saw that he ultimately lost that battle to Sir Ben so we know things can't end well for him.
VERA FARMIGA we've never seen before so we don't know what the hell she's gonna do.
ANTHONY ANDERSON we know was in Kangaroo Jack so we know that he's capable of doing anything.
ALEC BALDWIN we saw chew out Al Pacino in Glengarry Glen Ross and pull the rug out from under Leonardo in The Aviator. We saw him bomb Tokyo in Pearl Harbor, bomb Vietnam in Path to War and boss imaginary trains around in Thomas and the Magic Railroad. He boned Kim Basinger in The Getaway and Teri Hatcher in Heaven's Prisoners. Alec's no chump, he can take care of himself. Unless the bear from The Edge comes around, then he's screwed.
KEVIN CORRIGAN plays fuckups and losers. I mean that as a compliment.