Continuity mistake: When the girls start doing CPR on Cassie, there's a strand of hair running along her forehead. A shot later, it has a different style and is closer to the top of her head. (01:44:20)
Continuity mistake: After the bad biker bites Noel, he removes the rearview mirror from the windshield and smacks the bad biker with it. However, when Noel tells Katie to drive the car, in the exterior shots as she sideswipes another car, the rearview mirror is back up on the windshield; then it's off again. (00:33:35)
Revealing mistake: When Gary is being interviewed at the end, Slimer and the Dragon fly over them and away. However, Gary keeps staring at the entrance door; seemingly, the cue didn't work here. A shot later, from a different angle, he is suddenly looking ahead.
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."
Visible crew/equipment: At the start, when the giant egg falls next to Loann and she runs away, the camera and cameraman are reflected in the garage door. (00:00:54)
Continuity mistake: When Clay fights Anisette at the gas station, her heels change from stilettos to flats. Best visible when Clay throws her on a car, right after she says he should be retired.
Continuity mistake: When Lagrange finishes dancing with Argylle, she places both hands around his back, the left over the right. A shot later, they're placed the opposite way. (00:02:10)
Continuity mistake: When Deep Dark Secret breaks the jar to free the emotions, look at where the emotions are standing, and how the huge piece of glass lands behind them. In about three seconds, the piece of glass changes position, and some of the emotions switch places. (00:33:08)
Continuity mistake: During the party, Vanessa's grip on her cup differs between instant cuts.
Continuity mistake: When Axel introduces Serge, he places his hand next to his ear as if he were hard of hearing. From the opposite angle, his hand is lowered. As of then, the position of his hands is not continuous between shots.
Continuity mistake: Lady Raven arrives at the Coopers' place and starts talking to the wife. Cooper's watch is set to 1:35. An instant cut later it's set to 1:20.