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: In at least two scenes, cars from the 1990's can be seen, despite the fact that the film took place two decades earlier. (00:50:00)
Factual error: John Candy is at the top of the Calgary Tower having lunch. In the background you see a building called Bankers Hall which is slightly higher than the Calgary tower, that's fine except this was the 1988 Olympics, that building wasn't completed until late 1990.
Factual error: Although the movie is set in 1962, when Rodriguez jumps the fence of the junkyard, a red door from a '73-88 GM pickup can be seen in the background.