When Bud leaves the house to discuss getting a divorce with Krista, there is only one car parked at the house, a Nissan Pathfinder (Shaun's car). There is no car belonging to Bud parked in or around the house. Bud mentions he drives past the house on his way home from work. But where is the car, and how did he get there?
When the mother is taking the pillows off the bed she takes the same pillow off three times.
While at the Dean's house, Ashley asks Shaun about his brother's aspirin (drugs) and Shaun reacts shocked and nervous as if he somehow already knew she gave some to the Dean, but he was out in the car obtaining his transcript when she did that - so obviously he would not have known.
A deleted scene shows Ashley holding a different second dog while sitting in the backseat of Shaun's car.
When Shaun goes to ask his father for help in getting into Stanford, his father is wearing a grey sweater. A short while later he is wearing a black shirt.
At the end of the film when Shaun and his friends are on the beach, he decides to take up surfing again. Shaun and his friends pick up their surf boards and run towards the water. However, the sun is setting and the sea is really calm. There are no waves at all, not even a ripple.
At the end when they run to go surfing the sea is completely flat at sunset. Not one wave in sight.
When 'Lupe' is talking to Shaun, the subtitles read: 'Double pay on weekends?' while her mouth is saying 'OK'
Although the film is supposed to take place in Orange County, none of it was shot there. All locations are in Los Angeles County.
The kid talking to Ashley at the party mentions that he got 50 bonus points for his use of the word "mazer" in Scrabble. 50 bonus points are awarded only when a player uses all 7 of their letter tiles in a turn according to the official rules of Scrabble. While it is possible He played "Mazer" as the last play of the game using his remaining 5 tiles He would not have gotten a 50 point bonus for doing that.
When Lance is talking about his t-shirt idea, his hand moves across his chest the opposite way that the words would be going.