Director D. David Morin points out (DVD at 07:18) that Johnny's red on white Kurt Warner football jersey (02:15 to 06:58) turns into a white on red jersey (at around 4 mins) when he is in Dr. Drew Carter's office waiting for the doctor. David adds that the wardrobe lead (Nancy Terryn) was ill one day (about day 12 on the 15 day shoot) and he didn't notice the change. Apparently, that was the day the white jersey was used because at 31:34 when Johnny and Kayla start out on a bicycle montage and Johnny is in the red jersey, David notes the shot was taken on day one of the shoot when they hired a crane for the sweeping panorama. The only other white jersey shots are during Johnny's first day at school (40:15 to 41:03).
In the schoolroom at 41:37 when Michael gets up to tell what he wants to be when he grows up, he is seated fourth in a row with a curly haired boy in a blue short-sleeve shirt at the head of the row (41:32) who has a blond girl in braids and a blue shirt to his right and Johnny is nowhere in sight. But at 41:50 Johnny is at the head of the row (in a red jersey) with the curly haired boy behind him and the blonde girl in the blue shirt to Johnny's right.
After Mrs. Carter tells Kayla it is OK for them to play on the beach, both Kayla and Johnny are barefoot as they run down the sidewalk toward the beach (at around 36 mins), but, after a cut to Mrs. Carter dialing her phone, Johnny is wearing tennis shoes when he stagers briefly on the grass (at around 42 mins).
When Johnny gets up after spiting up blood on the beach (at around 19 mins) wires from his microphone can be seen under his shirt just above his jeans.