At the end of the scene where Boof is playing basketball with Scott's father, Boof leaves and Harold proceeds to play on his own. After his final shot he celebrates with both fists in the air, however his shot clearly hits the rim and bounces out.
During the beginning of the Championship, a soaking wet #23 (Doug Savant) is dramatically fouled. The coach then yells for a time out. Standing next to the assistant is none other than #23 with hair completely dry, complaining about the same foul that just injured him. The very next clip is #23 laying on floor, then he is helped to the bench.
When Scott comes out of the locker room for the big game and
talks to his coach, his face is dry. However, when he gets in the huddle, his face is obviously sweaty as if he's been playing, when in fact he's hasn't entered the game yet.
In the game against the Cadets (first game in which Scott turns into the wolf), Scott is fouled right after the opening tip-off. As this was not a shooting foul or the 6th foul committed by the Cadets, Scott would not have been awarded any free throws.
During the Surfing USA montage, during the sequence of back flips, if you look closely you can see a pair of handles on the roof of the van for the stuntman to hold onto. The most obvious angle is during the last back flip.
The goof items below may give away important plot points.
In the last scene, before the slow motion kicks in, when Scott's dad comes down from the bleachers you can see a girl in a red shirt and blue jeans. Her fly is unzipped and she finally realizes it and tries to pull her shirt down over it before zipping up her pants. When that doesn't work, she puts her jacket over her front side covering herself up.
In the very end shot after Boof and Scott hug, Pamela can be seen in the bottom left hand corner of the screen cheering and clapping with a guy in a brown jacket, then turning very sour faced after glancing towards the camera.
When a kid in the hardware store blows a dog whistle, our hero is noticeably affected by it, while his father drones on talking, unaffected. But later in the film it is revealed that his father is also a werewolf, so he should have been affected by the whistle.