Factual error: Jerry says that Flynn argued with Stephen Hawking regarding the thesis of Hawking's book when Flynn was only nine years old. However, Flynn celebrates his 32nd birthday in the movie in 2006, meaning he'd have been 9 in 1983 and 1984, while Hawking's first book, A Brief History of Time, wasn't published until 1988.
Factual error: In the scene following Flynn Carson's playful dual with the Excalibur sword, he is told that he is using the Shroud of Turin to wipe his face but when Flynn holds the cloth up for all to see, it is the Veil of Veronica, not the shroud. The veil is small and held only the face of Jesus Christ. The shroud is roughly 14 feet long and held Christ's full body image.