Trivia: During the scene where Kevin Bacon is shaving his head, director James Wan originally wanted to have Bacon wear a bald cap and wigs to shave the hair off, because he wanted to make sure there were no mistakes (in case multiple takes were required), and he felt bad about the idea of Bacon shaving his own hair into a patchy mess, and then having to keep it that way for the remainder of the shoot. Bacon felt he should shave his own hair so it would look realistic, and to help him get "into character" more. Bacon was eventually able to convince Wan to allow him to shave his own hair after persisting.
Trivia: When Kevin Bacon shoots down one of the thug's doors, he asks the guy where Billy is. The thug responds "the office" - it's during this scene where Kevin makes the thug call Billy. When Billy answers the phone, look behind him, you can see a face that resembles the Jigsaw Killer mask (it even has the red swirls on the cheeks), possibly paying tribute to the Saw series (2004 - 2010) because this film shares the same director, James Wan. (01:27:00)