In the commentary, the director and producer mention that many of the best lines in the film were improvised by Denzel Washington and Mark Wahlberg.
Paula Patton's second nude scene. It was her idea to go topless when she's in the bedroom with Denzel Washington, because she said it didn't make any sense why she'd have a bra on after they just had sex. She joked in an interview that it didn't make sense to have her panties on either, but she said there was only so far she'd commit to the scene. She appeared nude earlier in another movie where she acted along with Denzel Washington, called Déjà Vu.
During the film's development, Vince Vaughn was originally cast as Bobby, and Owen Wilson was originally cast as Stig.