- Ability over Appearance: Sofi was originally written for an Asian actress.
- Awesome, Dear Boy: Mark Wahlberg liked this script so much, he signed on before a director was hired.
- The Cast Showoff: Mark Wahlberg and Garrett Hedlund already knew how to iceskate.
- The Danza: Sofia Vergara as Sofi.
- Fake American: Chiwetel Ejiofor, who is British, plays Victor Sweet
- Playing Against Type: Chiwetel Ejiofor as a gangster.
- Stillborn Franchise: An article written in 2010 suggested that Paramount Pictures was developing a sequel for the film called Five Brothers, with Mark Wahlberg returning to reprise his role. It would be written by David Elliot and Paul Lovett.
- Throw It In!:
- When Jack is shot in the legs, Garrett Hedlund actually fell into the telephone pole, hitting his head. After the second take, his head was bleeding.
- Almost all of Mark Wahlberg's lines were improvised. Garrett Hedlund had difficulty improvising his lines, so John Singleton and Wahlberg helped him through it.
- What Could Have Been:
- Ben Affleck, Matt Damon and Ethan Hawke all turned down the part of Bobby. Hawke loved the script, but could not commit to it, because of scheduling conflicts. Damon and Affleck both said no, because they found the script to be "ultra-violent". Bradley Cooper, Vin Diesel and Jeremy Renner were also considered.
- In the first draft of the screenplay none of the brothers die. In the second draft, Jack is killed. The screenwriters thought that it would add more of an intense dislike for Victor Sweet, and a more emotional state of the rest of the brothers.
- In the original screenplay, Angel carried Sofi upstairs during the shootout, and placed her into a steel tub. John Singleton liked the idea, but it was dropped due to time.
Trivia / Four Brothers