Revealing mistake: This mistake, as far as I know, can only be seen in widescreen. After Rose, Jack, Tommy and Fabrizio have run on deck (after breaking the gate down), the camera looks down the ship toward the bow. If you look at this carefully, you can see city lights in the top-left hand corner of the picture. I know these are city lights because in a book about the movie, it shows a similar picture. Fixed on Blu-ray. (02:08:05)
Revealing mistake: When Cal shoots at Rose and Jack he hits a decorative wooden structure on top of a banister. When the piece falls apart you can see that it has been neatly cut in the middle, and you also see the explosive device that blew it apart. (02:14:40)
Revealing mistake: When Jack and Rose are running from the raging water that is gushing down the hall after them you can see the faces of the stunt doubles through the computer generated ones of Leonardo and Kate (slow motion can help but isn't essential). (02:17:15)
Revealing mistake: When Jack opens the gate after he retrieved the key from under the water we see that the water level in the background is lower, but the flow is towards the camera. It looks as if the shot has been reversed. (02:19:40)
Revealing mistake: When the boat is totally slanted sideways and Rose encounters Andrews, note the glasses and stuff over the fireplace and behind Rose. They don't slide downwards or move a single inch, defying the law of gravity, revealing the camera trick. (02:21:00)
Revealing mistake: The band decide to go their separate ways, just before the ship sinks. As they are seen departing, the lead violinist strikes up a solo - I think it'd be 'Nearer My God to Thee' or so the legend goes. A fraction of a second before he does, watch the second violinist - he disappears off to the right of the shot at first, then reappears near the side of the ship - he is obviously awaiting his cue as he turns round too early, i.e. before the lead strikes the first note, then turns away again. (02:24:15)
Revealing mistake: When the ship is sinking, there is a shot of Victor Garber leaning against the wall in deep contemplation. The camera angle is very tilted and a few things slide off the shelf in front of him. Look carefully on the DVD and you'll see a wire coming out under his arm behind him pulling the china cup off the shelf. Fixed on Blu-ray. (02:25:25)
Revealing mistake: Towards the end of the film when Titanic is gradually getting higher Rose and Jack finally make it to the top of the ship, watch closely at the shot when they approach the top of the ship and Rose grabs onto Jack. In the background right at the very top of the shot you can see many green screens stood at the top of the ship in the background where people are running around. (02:30:00)
Revealing mistake: In one of the sinking scenes, you can see the rectangular strobe lamps showing through the black fabric in the glass dome. (02:30:35)
Revealing mistake: In this scene, at the end of the film when Jack and Rose are hanging onto the railing, you can see the ship split in half, but when it drops, if you watch closely on the right side of the screen, you can see that the entire ship is still intact, the lifeboat cranes are visible all the way down the top of the ship. (02:35:10)
Revealing mistake: When the ship tilts to a vertical position, you see people falling and hitting objects on the deck. In a close up of that, you can see that a black and bronze-topped capstan has wrinkles in it and bends when someone hits it. Fixed in Blu-Ray version. (02:36:40)
Revealing mistake: Just after the Titanic has sunk, and all the people are thrashing around in the water; look towards the top of the screen as the camera pulls back, and you can see the back of the tank it was filmed in. It shows as a clear line against the background. (02:37:40)
Revealing mistake: As the ship is breaking apart, you can see the wires that pull people into the tear on the deck. (02:40:10)
Revealing mistake: In the engine room as the ship is sinking, the smoke and steam coming from the machinery rises at the same angle as the ship, about 45 degrees. So, the shot was filmed level, then tilted afterwards. (02:40:40)
Revealing mistake: In the scene where Rose lets go of Jack's hand and he sinks to the bottom, if you look closely enough, you can see Jack eyes move under his lids, even though he is supposed to be dead already.
Revealing mistake: When Rose and Jack first enter the boiler room, they run towards the right. If you look closely you can see the reflection of the worker in the back to the left in the mirror they use to make the bolier room look longer. In the next scene they are running in the opposite direction, because the set is so small due to the mirror, and once again you can see the same reflections caused by the mirror.
Revealing mistake: When Jack and Rose are talking at the bow of the ship before the "I'm flying" part, if you look at the windows behind them you can tell it is a painted prop area and not a real ship.
Revealing mistake: Just after Rose spits in Cal's face and runs off to find Jack, the camera goes into the water to show Jack through one of the portholes. In the external shot, it shows that the porthole is a good distance under the water. However, just as Jack says "Hello? Help me" you can see the water dip below the top of the pothole a number of times as it sloshes about.
Chosen answer: During the several years it took to construct the ship probably, or in any of the supplies/food brought on board, or in the furniture brought on board. A single pregnant female rat can be responsible for thousands of rats in a very short space of time (the offspring are not too choosy about who they breed with).
Soylent Purple
A pregnant female rat could have made a home in a underneath a third class couch and had the other rats then all the females would have baby rats quickly.