Character mistake: Gail reads right through Katie's poor excuse about crotcheting, and says she won't go to the ball "after what you pulled today with Guy." She did not do it (well she didn't do anything, but 'supposedly did') today, but yesterday. (00:31:00)
Character mistake: A detective (Briggs?) told Sonny, " that I was stupid enough to believe your dark fantasy NINE-ELEVEN call." [emphasis added] An American law enforcement officer, in particular, should know and use "nine-one-one" (911) when referring to the nationwide emergency telephone number. "Nine-eleven" (written 9/11 and NOT 911) is used to refer to the September eleventh (9/11/01) terrorist attacks in the U.S. (01:15:57)
Character mistake: When the posse is heading out in the morning, one guy says that it's heading north and they start riding in the direction he's pointing. However it's supposed to be first thing in the morning, and you can see the shadows of the horses cast to the left of screen while they are riding towards the camera. The sun rises in the east, which would be right of screen with the shadows cast towards the west. Since they are riding towards camera, this puts them heading south.
Character mistake: In the pivotal scene where Bolly and Jonah are explaining the need to replace their departing players in the aggregate, Jonah adds up 3 players on base percentage and divides by three. You can't get an accurate average for a rate stat by that means unless all the players had the same number of plate appearances, which they did not. The answer given by Jonah Hill is 14 points low. When the older scout questions it, Beane scolds him that he "didn't carry the one." Same mistake is in the book.