Revealing mistake: In the scene where Sarah (David's sister) punches one of the Delaney brothers after being harrassed in the alley, she draws back to throw a punch. She first bangs her hand on the brick wall then, after she throws the punch, she punches the other brick wall extremely hard. You can see her bend over whencing in pain and grabbing her hand right before they switch camera views. When they switch camera angles, she's no longer crouched over and she's obviously had time to recover. (01:37:15)
Revealing mistake: In the opening scene, when Jack is woken by the landlord, he slips into his natural British accent when he yells at the landlord and calls him "mad."