Continuity mistake: The green Alfa in the opening minutes has its side, and mirror, wiped out by a lorry. For the next 5 minutes it then drives around in perfect condition. (00:05:43)
Factual error: While handling the ignition coil cable to the distributor cap, Joe Pesci tells De Niro that the timing chain needs adjustment in his truck. A truck of that year with an inline Chevy motor would not have a timing chain at all, instead this truck would be equipped with a direct drive timing gear. Even if it had a timing chain, it would be behind the water pump and a cover. It would have been a several hour job to replace, not possible to adjust it.
Continuity mistake: When they finally arrive at the bottom of the sewer, Eddie's bandage is on a different cheek. (01:59:00)
Factual error: It is not possible that Pitt could have gone up to the ship when it was already blasting off. There was literally fire in the tunnel.
Factual error: Throughout the movie, scenes of the chess tournament room show the American flag incorrectly vertically hung (stars on blue upper left is proper), while the Soviet flag is correctly vertically hung. No real American vs. Soviet tournament would make that mistake.
Revealing mistake: When the Hårgas begin eating their meal after Dani is crowned May Queen, there is a shot of Dani just after the Hårgas pick up their knives and forks where she is looking over at Christian. Sitting next to her is a woman who cuts her food with a knife and fork, raises the fork to her mouth and takes a bite, but there is no food on the fork. She is just miming the actions. (02:13:15)
Visible crew/equipment: Opening sequence, Noomi Rapace kills all three terrorists who have arrived by truck, commandeers their truck and loads her two clients into it to transport them out of danger. As she drives away, we see a bare arm, hand and rolled up dress shirt of a person standing in the back of the "empty" truck. (00:05:05)
Continuity mistake: The IV bag has the name of Louie at first but then changes into something unidentifiable and then back to Louie again.
Revealing mistake: A major selling point of the movie is the CGI technology used to de-age Will Smith. The effect works for the most part of the movie, including scenes in daylight, but in the last handful of minutes, maybe because of the plain 'happy-ending' light used, maybe for budget reasons, the face of Junior is thoroughly unconvincing, with a dramatic drop in quality in textures and modelization. (01:44:30)
Continuity mistake: After Brandon finds out he arrived in the alien craft, he walks outside in the rain where he finally translates "Take The World" as his purpose. He continues on to Caitlyn's house to tell her what he has discovered and to give her a flower. When he arrives in her room, he is completely dry.
Other mistake: While in the pool room, Zoey falls off the wall onto a portion of floor that hasn't collapsed yet and loses consciousness. This area is next to the section of floor that collapsed first. Jason jumps down to help Zoey. As he is helping her up, and onto the wall, that section of floor collapses, forcing him to grab the wall to avoid falling 20-ish stories with the floor. As he looks down drop, the section of floor that fell first is amazingly back intact. (00:59:20)