Errors in geography: The train that cuts through the infield of the Hackensack stadium says "The Pine Tree Route", a slogan for the Maine Central railroad.
Errors in geography: In the opening scene, they're supposedly playing at Hackensack New Jersey's home field, but the wider shots clearly show mountain ranges beyond the ballpark.
Errors made by characters (possibly deliberate errors by the filmmakers): When Monty runs for mayor of NYC, the lawyers say that he is running TV ads in all 52 States. There are only 50 States in the USA.
Continuity: When Spike makes a profit of 10 million, Brewser ask to be alone. When they walk out the door closes and in the next frame they open the door and you hear the door close again.
Continuity: In the Yankees game, Ken Dixon's first at bat is as a left handed hitter. But when he hits the grand slam off of Monty, the TV shows a right handed batter hitting the home run. He could be a switch hitter, but he wouldn't face the same pitcher from both sides of the plate.
Factual errors: In the opening baseball scene when Brewster is facing Rudy, he is wearing a batting helmet with ear covers over both ears indicating he is a switch hitter. When facing Brewster, a right handed pitcher, he is batting right handed instead of left handed which would have been to his advantage.
Boom mic visible: The shadow of the boom mic can be seen moving on Salvino's left shoulder during the meeting with Heller.
Continuity: On the cover of USA Today it shows a picture of Monty Brewster in front of a podium with his "None of the Above" slogan. The article was to highlight the Yankees exhibition game, and before Brewster had decided to start his mayoral campaign.
Boom mic visible: (At 1:19) The tip of a boom mic is visible.
Plot holes: It is often regarded that Brewster using the "upside down airplane" stamp to mail a postcard is seen as a violation of the terms set down in the money spending clause the film revolves around. However, he was using the stamp for its intended use, so this wouldn't go against the terms of the will.