Continuity mistake: Flynn hits a line drive and a fielder makes a diving catch. The ball lands in the glove on his left hand. In the close-up, the glove has disappeared and the ball is in his bare hand.
Character mistake: In the "Casey At The Bat" sequence, the narrator says "The score is 4 to 2 with but an inning left to play." However, the scoreboard shows that eight and a half innings have been played, and only a half-inning remains.