When Christopher leaves his house to drive Jessica back to her grandmother's house, he is wearing a blue t-shirt and a red hoodie. The next day at the beach, he is wearing a white shirt and a blue hoodie, although claiming that he has not been able to go home since he can't get past the paparazzi.
At the scene where Jessica Olson and Christopher Wilde are sitting by the pond, there's no breeze when the camera's on Jessica, but there's a breeze when the camera's on Christopher. Then when Christopher sits besides Jessica, the breeze stops altogether.
Towards the end of the film when Christopher is on his laptop looking through pictures taken earlier with Jessica, the picture of the two in front of the Hollywood sign is seen from the movie camera's point of view. The disposable camera is obviously seen in the shot. If this photo were actually taken from the disposable camera, it would have been from a different point of view.
When Christopher and Jessica are driving in Jessica's grandmother's pink Pacer car, along the short-cut road (after escaping from the beach in California) a wheel trim (hub cap) comes off the car and rolls into the trees to the left of the car.
The hub cap magically reappears (seen when the car is sinking into the water/mud) a little while later.
When "Petunia" is sinking into the mud and Christopher and Jessica have scrambled clear, Jessica has lost her bag in the mud as she struggled out. Then there's a shot from behind them as they stand and watch the car disappearing under the mud and you can see Jessica's bag in Christopher's left hand. The next frame show them from the front and Jessica's bag has disappeared from Christopher's hand, and Jessica then realizes her bag is missing and she drops down to retrieve it from the mud.
In the scene where Christopher and Jessica leave the beach in Jessica's grandmother's car "Petunia" and are followed by the paparazzi, they end up on a dirt track. After shaking off the paparazzi, there is a long shot of "Petunia" coming up a slope in the road and you can see the hubcap separate from the front right wheel and roll away behind the car. As the car passes the camera position, you see the wheel is missing the hubcap. In a following shot the car is still traveling the dirt track and the hubcap has miraculously returned.
At the end when Christopher turns up and sings to Jessica he walks down the middle of the dance floor and from one shot you see everyone crowded around him and then in the next shot they're still walking towards him.
The drivers license shown for Sarah at the airport is the wrong type since she is under 21. It should have been vertical instead of horizontal; all minors (under 21) in the state of Michigan have been issued with vertical id's since July 1, 2003.