Factual error: Zippo lighters are sold dry, no fluid when new.
Factual error: For a baseball movie, you would think they would have known the rules of the game better. There is a scene in which Henry uses the "hidden ball trick" to pick a runner off of first base. He stands on the rubber on the mound with only the rosin bag in his hand while the first basemen holds the ball. It is a violation for him to stand on the rubber or straddle it without the ball in his hand and is called a "balk". Technically the runner should have been awarded second base.
Factual error: When Mr. Gaunt puts the jacket on Hugh, he says it's 1955 all over again. The flashback occurs and Jerry Lee Lewis' "Great Balls of Fire" is playing on the car stereo. However, "Great Balls of Fire" wasn't released until 1957.
Factual error: Phil departs from the office right after the 5pm news. Punxsutawney is over 90 minutes' drive from Pittsburgh. The sunset in Punxsutawney in early February is about 5.30pm, so by the time they get there it should be completely dark. But it's bright daylight, without even a hint of twilight. (00:05:45)
Factual error: When Thomas is at the race track and putting a bet down, the money he's holding is newer, even though the scene takes place in the 60s.
Factual error: Although taking place in North Dakota, the Jeep and cop car have the older Illinois plates.
Factual error: The movie feels the need to justify the fact that everyone in 1603 Japan happens to speak English (something most kid movies just gloss over) by explaining that they are trading with Great Britain, and therefore the locals picked up the language. That's real cute, but also blatantly false. Trade with the British empire was rather sparse, mostly with Dutch mediation, and knowledge of the English language was practically nonexistent - here, any peasant and even kids are practically bilingual.