During the scene when Jack pulls Rose into the exercize room watch the windows towards the back of the room past Jack. There are a few times when you can clearly make out a man in a white t-shirt. This of course was not a proper dress for back than...not to mention the cup of whatever he is holding.I guess a crew man wanted to make his mark. Watch the windows in several shots other than this and I can guarantee you'll see alot of white t-shirts.