It is impossible for Fiona to have "gotten" everything when Sam's father died. Under California intestate succession law, Sam would have been entitled to half of everything her father owned before he married Fiona.
When Brianna and Gabriella fall off the diving board, Carter gets splashed only on his right side. When he walks back to Sam, his whole body is wet.
The movie takes place during a drought, but the lawn by the gazebo where Sam and Austin dance is perfectly green instead of brown like all the other lawns.
When young Sam drives with her dad through town in 1994, a 2000 BMW X5 is on the side of the road.
When Sam is in Rhonda's house, she is looking through items in a red bowl and says, "Rhonda, you sure do have a knack for taking something simple and making it beautiful." The mask is not in front of the red bowl at this time. She walks over to Rhonda and looks at the dress with her. When the camera goes back to the red bowl, the mask is propped up against it, though neither Rhonda nor Sam had time to place it there.
The Northridge Quake happened around 4:30 a.m. There is no way that Sam's father would have been reading her a bedtime story at that time.
When Carter is setting a timer on Sam's cell phone, the cell phone screen is black meaning that the phone is off.
'The district attorney asks Fiona about her signature being on the witness line of her late husband's will, but witnesses are never legally allowed to be beneficiaries.' Fiona was not a beneficiary. Sam said she got everything, so Fiona would be allowed to sign as a witness. She didn't reveal that she knew Hal had a will, because then she would get everything.
The movie takes place during a drought.When they are racing back to the dinner after the dance, the road is wet.
When Brianna and Gabriella fight at the car wash - Gabriella is wearing earrings in one shot which disappear in the next shot.
The camera and a crew member can clearly be seen in Gabriela's car when she is practicing her "speech" at the gas station.
When David was introducing the bachelorettes to Austin, green tape marking where he should stand is visible.
Sam receives her acceptance letter to Princeton in early November, right after the Halloween dance. The earliest time Princeton would accept an application is November first, with notifications being mailed in early December.
When Sam hits the baseball over the fence, she does not follow through with the bat. Not only would the ball not go that far, the ball would have veered towards the right instead of the left towards Austin.
When Sam bumps into Terry at school, he walks away and says "Zion? Lieutenant Terry here", but his mouth doesn't move.
In the beginning, Sam says that she's graduating a year early, but later on she appears to be a senior.
At the football game at the end of the movie when the cheerleaders are in a line going down each one of the Fighting Frogs, on the other side of the field there is nobody in the stands not even a football team.
When Fiona is sitting on the tanning bed, the towel she is holding around her keeps shifting places between shots.
While Shelby and her two friends are walking through the hall saying "Move" repeatedly, Madison's yellow covered textbook goes from the binding facing out to the pages facing the camera then back so that the binding is facing the camera again.
The football used during the final game has a half stripe. Half stripe balls are used in collegiate athletics. High school balls have a full stripe around the ball.
In the scene where Carter hits the sign at the diner, it is obvious that a stunt driver is being used when the two cars are avoiding each other.
When Bobby and Eleanor are trying to convince Sam to go to the dance, Eleanor begins to say her next line too early, interrupting Bobby's line "put your freak on", about doing "whatever you kids do these days."
Towards the end of the movie, during the football game, if you look at the scoreboard it says period not quarter.
Sam's hair length and cut are different throughout the whole movie. When she is woken up at the beginning it is shorter and angled more, but when she is in the boy's locker room looking for Austin, it's long and with no angles.
In the baseball scene you can see the baseball has a face sketched on it before he places it in the pitching machine
When Fiona places the material from the Princeton acceptance letter under her arm as Sam enters the room, the bottom document is a brochure with color and graphics. When Sam leaves the room Fiona takes the material out and on the bottom is a plain white sheet of paper.
When Sam storms into the boys changing room to find Austin, as she walks past a metal screen there is a boom mic hanging down waiting for her to come around the corner.
All regulation high school football games across the nation only run in 12-minute quarters. The game starts the quarter with 15 minutes on the clock, the time limit played at the college and professional levels.
When Brianna and Gabriella are fighting in the car wash, Brianna jumps onto Gabriella's shoulders while soap starts spraying all over them. On the shots with the camera looking up at them, the soap is spraying on both of them, but when the camera goes to an overhead shot, the soap is only spraying on Gabriella.
When Austin comes into Sam's restaurant to get some coffee, Sam's hair changes from being in a long pony tail to in a loose bun pony tail.
At the end of the film, the position of the part of the shirt covering Fiona's left shoulder changes between shots.
After Sam receives her first text message from her "secret admirer" she tells Carter "I'll see you later" and turns to go the other direction. In the next cut, she turns around again.
When David is trying to get Shelby, and Carter tells him to back off, he brandishes his sword that has a round handle but when David snaps it, it has a flat handle.
When Carter and Sam are hurrying to get back to the diner, they pass the same Jiffy Lube and at least one of the same cars (the Volvo) in the background several times.
When Austin is asking Sam to the homecoming dance the book in the background keeps changing.
When Sam runs away from Austin you can see the bottom of her dress is brown with dirt, but when we see her run up the stairs shortly after, the bottom of her dress is pure white again
In the scene where Austin and his friends walk down the hall to post more signs for the lost cell phone, white tape to mark the beginning of their stroll is eventually visible.
When shooting sports scenes, the extras are moved from one side to the other depending where the camera is.
When everyone quits their Diner jobs, Brianna and Gabriella switch places from shot to shot many times.
When Sam walks into the pool yard to see Fiona, a shadow of a boom mic can be seen on the ground behind her.
When Brianna and Gabriella are at the car wash, Gabriella grabs a windshield squeegee. In the first shot, the plastic side is facing outwards, but when Brianna starts to run away, the squeegee is flipped so that the wet side is facing out.
When Austin is hanging a "looking for" poster in the high school, it moves around between shots of him talking to his friends.
If you look closer at the rejection letter Fiona forged, you can see she only changed the first line (a phrase along the lines of "mail in documents as soon as possible" is visible).
The address shown on Sam's and Austin's Princeton acceptance letters are different, and neither of them are actually the correct address.