Factual error: Here's a big historical mistake. The character of German Admiral Lütjens is depicted overall in this film as a wild-eyed Nazi fanatic. In real life, he was distinctly anti-Nazi, vehemently protested the anti-Semitic actions of Hitler's regime, and was himself subject to intense Nazi scrutiny as he was a quarter Jewish and his wife was half Jewish. He was one of many German naval officers who fought only for their country, not Hitler.
Factual error: Approximately 2 hours and 10 minutes into the "restored" full-length video version, there's a birthday party for little Lisa Dickinson, and the Alamo defenders sing "Happy Birthday" to her. The Alamo battle happened in 1836. According to David Ewen's "All the Years of American Popular Music," the song "Happy Birthday to You" was composed and copyrighted by sisters Patty and Mildred J. Hill, first as "Good Morning to All," in 1893.
Factual error: Jack Lemmon cooks spaghetti for Xmas dinner. On New Years Eve he picks up the tennis racket, through which he had poured the spaghetti, and one piece hangs limp from the racket. It would of course, have long dried and be hard as before cooking.
Factual error: The weaponry of the Romans and their use is wrong (as they are in all Hollywood movies playing in the Ancient Mediterranean that I know): Instead of one spear, each legionary would carry two weighted javelins, called Pila (singular: Pilum), which had a long narrow iron head. The purpose of these were to throw them at the enemy before melee; if they did not kill their targets, the pila would get stuck in their shields. The head shaft would bend, making the pila useless for 'return' to their original owners, and with the added weight of the javelin, the enemies' shields were rendered useless as well. Following this, the Romans attacked with short swords (the Gladii; singular Gladius).
Factual error: In the scene where nickels fall on newspapers announcing that Roosevelt beat Hoover, at least one of them appears to be a Jefferson. The election occurred in 1932. The first Jefferson nickel was minted in 1938.
Factual error: Considering the list of the ship (how far it's tilted in the water), its not until they make it to the upper deck that the passengers start acting as if the ship is tilting. Before they get to the top, they are walking normally, and the water is perfectly level with the floor.
Factual error: In the scene where Elizabeth Taylor is driving from New York City to Boston to start a new life, she drives over the Tappan Zee Bridge, from the Westchester County side toward the Rockland County side (heading east to west, you can tell from the location of the toll booths and from the way the bridge looks.) If she had left NYC by the Lincoln Tunnel, she would have had to cross the bridge going west to east. If she had left NYC via the Bronx, by far the more direct route, she shouldn't have gone over the TZ Bridge at all.