Continuity mistake: The name on Travis' helmet switches between 'Ryer' to 'Travis' several times throughout the movie.
Revealing mistake: During the shoot out with McGivens's gang at the Cortez ranch, the wife of Cortez sneaks out of the trap door with her baby and peers around the side of the building. You can notice that the baby is really a doll.
Continuity mistake: In the scene where the Griffins are having breakfast and Stewie is drunk, Brian has one egg on his plate, and some bacon. After Stewie jumps from the shelf, Brian has two eggs and no bacon.
Continuity mistake: After Train transports everyone across the narrow bridge over the lava, he slouches down to the ground in relief. In the next shot he is standing straight, looking normal.
Continuity mistake: When Valiant flies down the gun barrel, he takes off his backpack and helmet, and he lays them down in the barrel before squeezing through the back of the gun. When he comes back out through the gun with the other birds, the backpack and helmet are not there.
Factual error: In the first scene at the Pentagon, the sergeant tells the other officer that all satellites are being put into geosynchronous orbit to "hide them behind the planet." But objects in geosynchronous orbit don't remain hidden behind the Earth relative to the sun; they orbit once a day, remaining over a particular longitude on earth. Therefore, they would be subjected to the magnetic storms every day, during daylight at that longitude.
Visible crew/equipment: The cameraman is visible in Ben's sun glasses as he is video taping himself at the gas station.
Other mistake: When Dorthy is trying to audition for the Muppet's the man says they are gone and the Muppet's bus pulls up. If you look when the bus is pulling up there is no one in it, even the driver seat is empty. Then a few seconds after the bus stops Kermit and Miss. Piggy come walking out.
Deliberate mistake: The tiny hot air balloon that Francesca released in the debate room would never be able to support Casanova's weight.
Plot hole: The survivors find their way to the internet lounge to send out a message via email about the terrorist attack. The ship was upside down. All satellite dishes used to transmit over the internet were completely submerged in water. Even if there was power to the computers, they would not have been able to get a server connection let alone send out email.
Continuity mistake: When Beowulf enters the water cave and seeing Grendel's body, the initial shot has his right arm sitting next to him (most likely placed there after his mother's took it from the Meat Hall). When Beowulf leans over to touch Grendel's chest, the arm is gone.
Visible crew/equipment: Near the very end of the film when Tommy Lee Jones is standing in the ruined building surveying the scene where Melquiades is to be buried, a crew member in a blue shirt can be seen crouching down against the wall in the background.
Other mistake: Just after the pirates flee the island and the octopus attacks them: a white and green fishing boat can be seen in the top right corner.