Continuity mistake: When the girl gives Litwak her phone to show him there is a replacement part on eBay, her phones shows that it is connected to WiFi. Litwak doesn't set up his router until later that evening, he has only plugged it in. (00:09:41)
Suggested correction: It's possible she's either connected to wifi at another nearby business, using a public wifi signal, or using a friend's phone as a hotspot.
Other mistake: When Elastigirl is chasing the high-speed train, as she is in the middle of making her second final jump to reach the train, if one were to look closely, the train actually drives right past her before she lands. (00:31:40)
Plot hole: As shown when Robin comes under the influence of Slade's mind control device, the hypnotized people retain their abilities and higher intelligence, just with a loyalty to Slade. That being said, when Slade hypnotizes all the DC heroes, Superman and The Flash are among them in the theater. Slade orders all the heroes to chase after and destroy the Teen Titans. The Titans take off on foot with the others running after them and are able to keep their distance in a big chase sequence. Superman and The Flash never use their super speed to over take the Titans, which would have been so very easy.
Continuity mistake: The blue paint blob on the painting changes between shots. (00:47:00)
Continuity mistake: During the fight at Aunt May's house, May knocks Tombstone out of the house with a bat. The subsequent shots have him back in the house.
Continuity mistake: In the space shuttle, as the astronauts are preparing to leave and avoid the asteroid, the one in the front left seat is fiddling around with some controls and raises and lowers his arm. It is a smooth animation of his arm each time it moves. He lowers it back down and then the one behind him mentions the bay doors are still open, and then suddenly the guy in front's arm just jumps back up to its previous position instantly like a jump cut. (00:23:00)
Other mistake: Constantine is driving along a road and an big rig truck is heading for him head on. The truck honks and they both hit the brakes, stopping just a foot away from each other. But at the speed the truck was moving it could not have possibly stopped so quickly. It would have skidded into Constantine's car. (00:35:00)
Continuity mistake: When Jason lunges at Batman with his knife, there is a pile of garbage by the wall where he lands. In the first shot the barrel by the garbage is wooden. But in the next shot it's suddenly a metal barrel/drum. It then changes back to a wooden barrel again. (00:04:20)
Continuity mistake: Princess Dawn is in her chambers and her servants are preparing her for the coronation. When her book-headed valet tells her "You have come of age", he is suddenly holding the tome with both hands, while he had just one on it before the cut. (00:19:30)