Revealing mistake: When the Doctor travels back in time after being shot by the stone Dalek, falls down the stairs and tells himself that he has 12 minutes to live we never see either of the 2 Doctors' faces onscreen at the same time, and if you look at the hair on the Doctor that's dying it is completely different to Matt Smith's. That's because it is Gordon Seed, Matt Smith's stunt double.
Continuity mistake: When the crack in time appearing on the TARDIS' scanner is shown in the "Previously On" segment, the crack is depicted as extending into the leather casing, whereas in the scene in "The Pandorica Opens" where it appeared, it was confined to the screen. (00:00:57)
Factual error: When the Doctor, Amy and Rory are on the roof and the Doctor says "The question for now is total event collapse means that every star in the universe never happened", the Gherkin can be seen in the background. However, the Gherkin wasn't built until 2003, whereas this episode takes place in 1996. (00:22:40)
Revealing mistake: In the museum after the Doctor, Amy, young Amy and Rory escape the Stone Dalek, the Doctor uses the Vortex Manipulator to go back in time to tell Rory in 102 AD to let him out of the Pandorica. The third time he goes back, Amy moves despite being dead. (00:19:38)