During the Cowboys last possession when the film is going in slow motion, you hear the quarterback yell "Down... Go!" When the camera pans to his face, it's obvious that he is mouthing "set", not "go".
In the coffee shop when one of the old timers is writing down the odds on the upcoming game, he writes + 40 points under the Cowboys as they are the heavy favorite to win the game. He should have wrote -40 points. The way he writes it would make the Cowboys the underdog; getting 40 points.
During the practice when Spike is taken by his father and Kevin O'Shea to be a Cowboy, he yells at the tubby kid in the Darth Vadar helmet who is wearing a white striped shirt. Within seconds he is wearing a blue and red long sleeve shirt.
Hanon sticks his hands to the front of his jersey. As he runs for the ball, it hits him in the back and his hand is visible on the left side of his body, but when he is lying on the ground, his hand is stuck to his jersey again.
At the car wash when Debbie approaches Junior in the mid shot, he throws a white towel behind him onto a box, but the towel slips off onto the ground. In the close-up of their mini "water fight," the towel has jumped back onto the box.
When Bruce Smith asks the kids to show their intimidating game faces, he growls and flexes his arms in a crab pose (arms down). The immediate next shot shows him from behind, now suddenly flexed in a double bicep pose (arms up) as the kids run away.
Jake comes bubble wrapped to practice and the others start pushing him in the their circle. He hits the pole face first, but the next shot shows I'm sliding down the pole with his back towards the pole.
In football when it is a turnover on downs, the opposing team gets the ball back at the exact location of where the ball ends at the last play. On the Cowboys last possession Spike gets a few inches from the endzone, but when Giants have the ball, they start from the 20-yard line.
On the final drive for the Cowboys, they make it to, roughly, the 10 yard line after a long run - gaining a first down. They then only run 2 plays before the ball is turned over. It should have only been 3rd down after they ran their toss (where Spike is tackled inches from the end zone and the ball is turned over).
When Kevin O'Shea's wife and daughters are watching the home video of his tackle gone awry, what they are watching is obviously from the film, complete with different angles and shots of him from outside. His daughter could not have caught it all with the camcorder.