Ethan Hawke, Matt Damon and Ben Affleck all turned down the part of Bobby. The part eventually went to Mark Wahlberg. Ethan Hawke loved the script but could not commit to it because of scheduling conflicts. Matt Damon and Ben Affleck both said no because they found the script to be "ultra-violent".
The bathroom scene took 2 days to shoot. For 12 hours a day, Mark Wahlberg rested his bare bottom on a cold toilet, Garrett Hedlund stood in a hot shower, and Tyrese Gibson wore nothing but a robe. Mark Wahlberg had to be helped off the toilet at the end of each day, and Garrett Hedlund's skin peeled and pruned.
Mark Wahlberg plays a character named Bobby Mercer. There was a baseball player named Bobby Murcer who famously played for the New York Yankees during parts of the 60's, 70's and 80's. Mark Wahlberg is a fan of the Boston Red Sox, the rival team of the Yankees.
The trivia items below may give away important plot points.
In the first draft of the screenplay none of the brothers dies. 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.