Factual error: In the 1998 part of the movie, before the launch of the iMac, Steve is wearing his trademark black turtleneck and jeans for the presentation. At the actual launch in 1998, Steve wore a suit.
Continuity mistake: When he fights Chuck Lidell, he is wounded on the right side of his body. During a scene when he is lying on his side, the wound has moved to his left side and then magically reappears back on his right when he stands up.
Continuity mistake: When the movie begins, Mal's hair swaps between being dark and light purple.
Continuity mistake: When the woman is eating the bread roll on the train, the end of the roll switches from uneaten to having bites taken out of it and back again.
Continuity mistake: In the early scene, when Maura is talking to the man in the corner, that she thinks is homeless, she stands up and has a green bag on her shoulder. When she asks for the sunscreen back, there is no sign of her bag. Then it's back on her shoulder.
Revealing mistake: Right at the beginning of the film "rain" is falling on the car the camera shows before it moves to focus into the tunnel. However, look at the cars behind it, they aren't wet at all and it's visibly sunny. It's water being poured onto the car directly in front of the camera.
Plot hole: They have to invent Nitrotrinadium when they travel to the future because it was not invented yet, but was in the Russian drink in 2010, so should have already been available when they travel to the future.
Factual error: When he is in the restaurant and looking at the security feed, he does a who command when it should be "whois". Also the IP is incorrect - the 3rd octet is 265, despite the maximum possible value being 255.
Deliberate mistake: When Quinn is texting the boy next door, he responds too quickly for it to be real. She sends the "So you think I can stop traffic, huh?" text and gets a response within literally two seconds. She then sends the "Did I wake you up?" text and gets two responses within five seconds. Texts usually take several seconds (at least) to be delivered and opened, so even with great service and lightning-fast fingers, this is obviously far too quick.
Factual error: Near the end, Jackie Chan's vastly-outnumbered forces resort to throwing stones to somehow utterly destroy a phalanx of Roman legionnaires in close-quarter combat. This scene flies in the face of what we know about Roman military superiority in the time of Tiberius. The Roman Army was the best-trained, best-organized, best-equipped military force of the Ancient World, specializing in tireless close-quarter combat and impenetrable defense. To suggest that Jackie Chan's frantic and disorganized group of fighters (throwing stones by hand) might overcome Roman legionnaires is like suggesting that cave men might overcome the modern U.S. Marine Corps.
Visible crew/equipment: When Bryson and Katz are getting onto the Greyhound bus, a guy in a fluorescent jacket can be seen holding traffic up in the distance whilst the scene is filmed.
Continuity mistake: At the end, the TV newscaster reports that 150,000 reserve human forces have been activated. But the crawl strip at the bottom of the screen reads "150,000 RESERVED human forces," a different meaning altogether. (01:59:00)
Continuity mistake: When Bianca takes Wes to the "thinking rock", as they talk and her hands are in her lap, her hair moves from over her left ear to behind her left ear and back, twice.
Continuity mistake: When Gordo leaves Simon and Robyn for a few minutes to handle a work thing, Simon starts mocking Gordo in his absence. Simon tells Robyn that Gordo wants to nail her and Robyn says "Stop it," but Simon continues his mocking of Gordo. At the end when Simon is listening to the recording that Gordo made of that conversation, Robyn's "Stop it" is absent.
Other mistake: When Marry Anne flies into the dark forest for the first time she drops the boutonniere. After seeing the primrose petal she flies off empty handed but has the boutonniere later when she meets Roland.
Character mistake: The poster on the wall near the start reads "Our Egg Donor's [sic.] are helping to fulfill the dreams of women across America." There is an unnecessary apostrophe in the word "Donor's." (00:10:05)
Other mistake: Ma and Jack bake a cake, but there is no way of doing this as they have no oven - only a work top hob and a grill.
Factual error: Jack could not be demoted from sergeant to corporal by his CO. Substantive NCOs can only be demoted by court martial. As aircrew, his rank of sergeant would be a substantive rank, not an acting one (since it was the minimum rank for aircrew). And rank chevrons were made in one piece (two for a corporal, three for a sergeant), so if he was demoted he would have a new set of chevrons, not the top chevron removed as depicted (not only would this be impossible, but it would be a clear indicator that he'd done wrong and given he is still an NCO this would be demeaning).
Continuity mistake: Near the beginning of the movie when Joy is in her airline's company uniform and getting ready to go to work, the knot on her scarf changes from loose to tight several times in the different shots.
Factual error: The delivery van bringing gear for the walk has a 718 area code on it. That area code did not exist until 1984.