Continuity mistake: When Rose and Jack run through the dining room with Cal shooting them, notice that the floor is tilted to reflect the ship sinking. In the next scene when they run down the stairs, the floor is now perfectly level. There is no tilt to the floor. Notice how the water tumbles out of the door - it falls on a flat surface and disperses evenly with no angle to it. (02:16:05)
Continuity mistake: When Cal confronts Rose and Jack at the last lifeboat, once in a while when the camera is only on Cal, it looks like it is raining lightly, however, it is dry in all other shots facing others. (02:16:40)
Revealing mistake: In the scene after Jack and Rose try to save the child from the Italian guy, when the water bursts through the doors, they run away from it. But take a close look at Jack's neck: you can see the edge of a black wetsuit. And under his entire shirt, it's a little darker than it is a few moments later when they try to open the gate. (02:16:45)
Continuity mistake: After being shot at by Cal, Rose and Jack race down the hallways outrunning the rising water. Rose is wearing white sneakers, yet she is seen two minutes later wearing period shoes when Jack retrieves the gate key that the crewman dropped beneath the rising water. (02:17:05 - 02:18:50)
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)
Factual error: The movie shows men removing the boats that have been stowed (Collapsibles A - D). The boats that they remove are not collapsibles, which were wooden bottom boats with rolled down collapsible sides (hence the name). (02:18:10)
Deliberate mistake: Even though the movie uses the correct number of rockets, the timing is awful. The last rocket was fired at 1:40 AM at the latest. In the movie, the last rocket is fired when the last boat to be lowered on the davits leaves (the one Rose gets, and jumps off of). This would make it 2:05 in James Cameron's Titanic time. It was probably changed to add more drama to that heart-throbbing scene... (02:18:30)
Continuity mistake: When Rose and Jack beg a steward to open the gate for them while the water is rising, the steward drops the keys and runs away. There are two shots of the keys on the chain lying in the water arranged in totally different ways (the difference is not caused by the water flow as the keys are not moving in either shot). (02:18:55)
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)
Continuity mistake: When Will kills Tommy and commits suicide, the number of dollar bills on the floor next to Tommy's foot change number and position between shots. (02:19:40)
Continuity mistake: In the scene close to the end, we see crewmen of the ship pulling down a lifeboat, if you watch closely the plank that passengers sit on breaks off when falling onto the deck, but in the following scene it has repaired itself and is back on the lifeboat. (02:20:10)
Factual error: Rose and Jack retreat aft of the 3rd funnel while D deck (1st class dining salon between funnel 2 & 3) is being flooded. They go down to E deck, which floods then they come back up to D to the locked gate, then escape to C deck just as D floods to the top. The 1st class dining salon extended across the entire width of the ship, so D deck was flooded to ceiling aft of 3rd funnel at the time they escaped below decks. In reality, if the ship were flooded that high, only the stern would be sticking above water. The 'split' did not even show the water that high and far back in the ship. (02:20:25 - 02:25:30)
Visible crew/equipment: When Jack and Rose are running away from Cal to the first class dining room, if you look at the glass you can see a black screen, a light, and a crewman. Fixed in the Blu-ray version. (02:20:32)
Factual error: Both times the fireplace in the first class lounge is seen there is nothing on the mantlepiece. But in photos of the actual lounge there is a statue on the mantle called "Artemis of Versailles" which was a small copy of the original in the Louvre, Paris. The statue was even photographed on the ocean floor when the Titanic was found, but there is no statue in James Cameron's movie. (02:20:40)
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)
Visible crew/equipment: When the captain goes to the wheelhouse, which is flooding, you can see the shadow of a camera at the bottom left corner. (02:22:10)
Continuity mistake: Captain Smith is drowning. In one shot, the window busts and water leaks into the room with the steering wheel. In the next shot, the window is fully intact and breaks again. (02:22:50)
Continuity mistake: When the captain looks at the bridge sinking, the water level is by the middle of the helm wheel. In the next shot, from the other entrance, the level is lower than that, and in the next it's again by the middle of the wheel, which is also turned to a different position. (02:24:00)
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)
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.