When playing football with the Chief, Johnnys hand is handcuffed behind his back. When Big Cheese runs off with the ball and they chase him, his hand is no longer handcuffed.
When Johnny is playing the drums during the credits, the Charlie Chaplin image on the poster in the background starts out looking to the right and Johnny's hi-hat cymbal is on the left. During subsequent shots back to this scene, the poster and the hi-hat cymbal reverse position several times (i.e., the image in the poster looks to the left then to the right, the hi-hat cymbal appears on the right and then on the left.).
When Coach Hisler goes to visit Piermont (waiting for Johnny to show) he takes a bus but when he makes a phone call to find out where Johnny is he tells Wallace Gibson that the airport was a madhouse. Then he tells Johnny on the fake phone call "As soon as I get off the airplane I will come see you"
A cop is thrown through the windshield of a cop car. The glass breaks in big shards like plate glass. Windshields are made from laminated safety glass and shatter into small pieces that stay together.