Brad Pitt was reportedly set for the Damon part, dropped out, and produced instead.
Ray Leota was reportedly set for Dignam but could not do it.
Denis Leary was the next reported Dignam possibility and also could not do it.
Al Pacino was the first reported Costello choice and is debated as an alternate.
Robert De Niro reportedly declined Queenan to make The Good Shepherd.
Mel Gibson reportedly could not play the Alec Baldwin part because he was filming Apocalypto.
RZA was reportedly offered the Anthony Anderson role.
Nicholson’s proposed prostitute scene and retained dildo improvisation are presented with explicit uncertainty.

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Winstone and Nicholson’s friction, Nicholson’s Red Sox/Celtics refusal, DiCaprio’s project choice, accent coach Jay Giannone, profanity, and Wahlberg drawing on people who arrested him

In the discussion (6)

Approx. transcript time · 00:28:40Read transcript

Ray Winstone reportedly said he and Nicholson did not get along during filming.
Nicholson reportedly refused a Red Sox hat and banned Celtics hats on set.
DiCaprio left The Good Shepherd to make The Departed.
DiCaprio’s Boston accent coach is named as Jay Giannone.
The film is reported to use “fuck” or derivatives 238 times.
Wahlberg reportedly based Dignam on a compilation of people who arrested him as a youth.

Costigan accepting undercover erasure, the impossible statehouse view, the central romance, Madolyn’s inaction, an intentionally forgettable killer, Queenan missing Sullivan, and the literal final rat

In the discussion (7)

Approx. transcript time · 00:38:32Read transcript

Costigan’s willingness to accept the undercover assignment and identity erasure is questioned.
Damon’s character’s impossible statehouse apartment view is questioned.
Whether Costigan and the doctor would get together is questioned and then accepted through a larger reading of Costigan and Damon’s character as opposing ways of living.
the doctor not turning Damon’s character in after Costigan’s death is questioned.
Casting a forgettable actor as Costigan’s killer is debated against using a more famous face that would telegraph his purpose.
Queenan’s failure to suspect Damon’s character despite obvious suspicious behavior is questioned.
The literal rat at the end is criticized as an overly explicit symbol, then partly defended as a closing bow.