Continuity mistake: After Lucius kills the wild monkey, he's got blood all over his mouth, beard, chin, and neck. When he stands up, he's spotless.
Revealing mistake: Before the big battle between Lucius and Acacius begins, the soldiers arrive at the bleachers, where we see several shots of the people. Check the crowd, and you'll notice it's a flipped shot of the previous people. (01:33:32)
Deliberate mistake: When Lucius is shown Maximus' tomb, the painting on the wall reads, "What we do in life echoes in eternity," in plain perfect modern English language. Of course, it helps audiences relate to the first movie, but it's ludicrous, to say the least.
Factual error: After the naval battle, Thraex is waiting for an informant who tips him off about Lucilla and Marcus Acacius's plans. And of course, as a well-educated gentleman of 200 AD, he kills time by reading the newspaper. Wait, what? Needless to say (to anyone but Ridley Scott, probably), ancient Romans wouldn't/couldn't exactly get their news by newspaper, the press having not been invented yet. This one looks so modern in its layout it even has headlines and a proper publication title, "Roma Viridia."
Revealing mistake: During the naval battle, after an underwater shot of a man being eaten by a shark, check the poop deck on the left, and you'll notice a bulky floor with wrinkles around where people fighting and falling bounce on, revealing a tarp hiding a safety mat.
Character mistake: When Lucius holds his wife's corpse in the sea, a wave crashes against her and splashes her face. The actress can't help wincing.
Continuity mistake: Glyceo grabs the sword on the arena floor and extends his right arm. An instant cut later, his arm is lowered, then it cuts back to the previous angle of his arm extended.
Continuity mistake: When Lucius steps in the water to see his wife's corpse, his hairstyle around the forehead changes between shots before he is splashed by water.
Continuity mistake: After Lucius quotes Virgil, he kills a man who collapses on a chair. When he lies dead, there's a leg or armrest on the floor parallel to his body. A shot later, it's perpendicular.
Continuity mistake: When Lucius addresses both armies at the city entry, he throws his sword on the floor ahead of him. He walks around, and from the opposite front angle, one can see the sword behind him. From the immediate opposite angle of his back, the sword is gone.
Continuity mistake: After the Virgil quote scene and the fight that follows, Lucius takes a bath. There's a close-up of him saying something about dying in the arena, and his hair is suddenly better brushed and drier. Then it goes back to the previous wet hairstyle.
