NOTE: This spoiler was sent in by Brentage5000who says... "This flick was really a lot better than I thought it'd be; kind of a mix of You've got Mail and Cinderella."
The movie starts with Sam Waters (Hilary Duff) narrating about how a short time ago, in the San Fernando valley, she and her father (Whip Hubley) were real happy together. They were like best friends, always having fun, and even though she was always a little behind in the make-up and fashion departments, it just didn't matter, because she had her father and her dad's workers at his sports themed diner. She was totally satisfied, but her dad thought she needed one more thing, so he got married to Fiona (Jennifer Coolidge), who brought with her two evil little stepsisters for Sam. Things go along though, until one night when Sam's dad is reading her the story of Cinderella and she asks if fairy tales come true. He says no, but dreams do, and says his dream is for her to go to college. When she asks where princesses go, he stammers and says, "Well, where princes do, at Prince ton - Princeton." She smiles as he tells her that a lot of answers to life's questions can be found in this fairy-tale book (important), and then an earthquake starts up, breaking a beautiful snowglobe she had and killing him. Since they couldn't find a will, Fiona got everything, so now Sam lives in the attic of her own house, the diner is 50s-themed instead of sports-themed, and Sam has to face life without her best friend.
Eight years later, Fiona wakes Sam up through an intercom system and tells her to bring her breakfast. Sam goes out to the pool where her stepsisters, Brianna (Madeline Zima) and Gabriela (Andrea Avery), are doing a synchronized swimming routine, at least until one of them farts in the other's general direction. Fiona tells Sam to get down to the diner and help out, but Sam says that she has a test at school. Fiona tells her that school is for getting a job, and she has a job, so it's like skipping a step. Exasperated, Sam heads for her car when the sprinklers turn on. Sam begs Fiona to turn them off since they're in a drought, but Fiona says that since droughts are for poor people and they're rich, that doesn't apply. Sam leaves, and we see that they're the only green lawn in a city full of brown lawns.
At the diner, Sam is busily bussing tables on roller skates when Rhonda (Regina King), the head waitress and last remaining link of sanity in the place, comes up and tells Sam to get out of there and go to her test. Sam gratefully obeys and goes to pick up her best friend Carter (Dan Byrd), an aspiring actor and small-time freak whose totaled three cars that his parents have brought for him. They head to school, get cut off for parking spaces, get hassled over Sam's working at the diner (one of the football players, Dave (Brad Bufanda) asks Sam for a breakfast burrito), and get mad at the two biggest Alpha-types in school, head cheerleader Shelby (Julie Gonzalo) and head football player Austin Ames (Chad Michael Murray). Anyway, Sam and Carter get into school where the school-radios wannabe-shock-jock DJ (Aimee Lynn Chadwick) is broadcasting news about the upcoming Halloween dance and commenting how stupid it is until the teacher liaison comes in and has her going "I pledge allegiance to the flag, etc, etc." In the halls, Sam and Arty bump into Terry (Simon Helberg) a freak that lives in a fantasy world of every sci-fi film ever made. Sam is happy for him and his world and says so just as she gets a message on her phone from a guy named "Nomad069." "Ah, yes, speaking of fantasies" drawls Carter as Sam rushes to a bench and starts IMing back and forth with Nomad as "PrincetonGrl" (they met in a Princeton chat room) which ends up lasting all day and long into the night. They talk about Nomad's dad, who has pretty much his whole future planned, play football for USC, then follow his dad into the family business. Nomad asks Sam to meet him under the ball in the middle of the floor at the Halloween ball, and she agrees to it. Before they sign off, Nomad slips Sam some Tennyson, and we pull back and see that Nomad is Austin Ames.
The next day, Sam and Carter are out on the baseball field with a pitching machine and Sam is complaining about how Fiona won't let her go to the ball (sound familiar?). Carter tries calming her down, mostly to avoid getting hit by Sam's wayward hits, which all hit parts of his body but doesn't do that well. On the last ball before Sam has to head for the diner, Sam pictures the ball as Fiona's head and hits it all the way over to the football field right next to Austin's foot as he's tossing the football with Dave. Dave is impressed that a girl hit that, and Austin tosses it back, shouting "You're welcome!"
Later, at Austin's dad's auto-detailing place, Austin is looking at some Princeton brochure when his dad (Kevin Kilner) comes in, spouts off some "your-future-is-all-set-don't-screw-it-up" line, then tells him to go wait on a customer, Sam. His first line when he gets to the car, "You need a wax." She thinks he means her, but of course he meant the car and gives her a slip to give to the guys inside. The stepsisters pull up then and start insulting Sam but end up fighting with each other. Sam gets the car done and heads for the house with some of Fiona's dry cleaning. When she gets there, Fiona is lying in a tanning bed, but she comes out of it long enough to tell Sam she can't go to the ball and that Sam's not very pretty, and not very bright. Defeated, Sam heads for the diner where her first customers of the day are Austin, Shelby, and their troupes. Sam comes to take their order, and Amber asks if they have anything with no carbs, no sugar, and no fat. Sam answers her with, "Water," making Austin laugh a little and ruffling some of Shelby's feathers. Regardless, she orders some iced tea and Dave orders a Coke and reminds her that he's still waiting on that burrito. Sam leaves, and Austin chooses that moment to break up with Shelby, saying he's in love with someone else, even though he doesn't know who. Shelby's troupe storms out, followed shortly by Dave and Austin's other friend. Sam comes back with the drinks, and Austin offers to pay, but she tells him forget it.
A little while later, Fiona comes in with the twins, bosses everyone around, and says she'll be back by midnight with the girls. She leaves, and Rhonda tells Sam that she should be going too. This is strengthened by Carter, who comes in wearing a Zorro costume and driving his dad's Mercedes. Eventually Sam caves, but says she doesn't have anything to wear. Rhonda grabs her and Carter and they head for a costume shop. Rhonda promises the owner free breakfast for a month, and they get in. While Carter plays with various accessories (e.g., knife through his head = That outfits a killer, Sam!!) and Sam tries on different costumes (matador, hula dancer, genie, knight, Porky the Pig), Rhonda sees a little white eye mask on display. The shop owner says he doesn't have anything that goes with that, but Rhonda says that she does.
At Rhonda's, Carter is waiting outside while Sam is being given a dress by Rhonda that she was saving for her next trip down the aisle ("Long story, don't ask" she says). Sam gets the dress on (offscreen) and her and Carter head for the ball, where DJ has things in full swing. The twins get there dressed as a Siamese twin-cat, and Austin is dressed (naturally) as Prince Charming, which kinda ruins the "3 Musketeers" thing that him and his pals were planning on. Sam and Arty pull up out front and Sam is a little worried about this, so she gives Arty her phone and he sets it for 11:45 so they'll be back at the diner in time. She goes in, and some slow music starts playing as everyone sees this gorgeous girl that none of them know standing on top of the stairs. Shelby quips, "Love her dress, hate her," as Sam starts down towards the floor while Austin watches from afar (well, not that far). She gets under the ball and is addressed from behind with "At last, destiny has brought us together." She smiles, turns, and Terry? Terry, dressed as Neo from The Matrix, comes and starts dancing with her to her dismay until Prince Austin comes up and saves her (Mr. Anderson he says threateningly, hinting that Terry should leave yesterday). Sam recognizes him and doesn't believe it until he reminds her of the poetry thing and a little bit he wrote her during one session. They go outside as one costume judge observes them approvingly.
While Austin and "PrincetonGrl" are outside, a slightly drunk Dave is hitting on Shelby. Meanwhile, Sam has conceded to give Austin ten questions to guess who she is. He learns that she does go to their high school, she likes Big Macs over salad, she voted for him for student president, she doesn't think he's ugly, she wasn't disappointed at discovering who he was, and that she'll dance with him without music. We see him ask one more question. "Do you believe in love at first sight?" to which she says "I'll let you know." They move to kiss, and right then the alarm goes off. She jets, saying she's late for reality, grabs Arty, and is interrupted by the announcing of the winners for best costume, her and Austin. She doesn't stop, though, and keeps running for the exit, dropping her cell phone on the way out, which Austin picks up as everyone looks on.
Once back in Carter's dad's car, Carter asks Sam how it went, and she says good except for where she had to leave before telling Austin who she was. Elsewhere, Brianna and Gabriella are piling into Fiona's car prizeless. Both cars head for the diner and pull up alongside one another. The twins look and see Sam in Carter's car, but Sam ducks before Fiona can look, so she just sees Arty looking stupid. They pull away and Sam sits bolt upright panicked, and they race for the diner although considering Carter won't go over the speed limit out of fear and Fiona has no control of the car, it's not much of a race. Anyway, Fiona gets back to the diner, and Rhonda and the other workers try stalling her with various nonsense questions until she demands to see Sam who suddenly pops up from the kitchen with an order. The cook says he was teaching her how to make pancakes with salmon in them. Fiona frowns and says that something stinks around here besides the salmon but she leaves anyway, dragging two very confused stepsisters behind her. Once she's gone, Sam breathes a sigh of relief and sits down, still wearing her gown underneath the black shirt she has to wear for a uniform. Outside, Carter is looking the Mercedes over for dents and is utterly relieved over the lack of any. He starts to pull out at the same time as Fiona and the girls and just slightly bumps the sign post supporting the sign bearing the name of the place. This slight bump, however, is enough to bring the whole sign crashing down on top of his dad's car.
Next Monday (the dance was on a Friday), Carter tells Sam that he's grounded forever and asks if she's gonna tell Austin who she is. She says Austin's probably forgotten all about her right before seeing hundreds of Have you seen "Cinderella" signs posted everywhere. Carter thinks this is good and that she's got to tell him, but she fires back asking if he's gonna tell Shelby who Zorro was. They make a deal, he tells Shelby that he's Zorro, and she'll tell Austin she's Cinderella. Cut to Austin and co., who are posting signs up, even though the pals don't think it's that great an idea until they start thinking things like "Hey, maybe she's a foreign exchange student dude, that is so HOT!" Back with Sam and Arty, they are poolside and watching Amber gush over Zorro to her pals as the twins do their thing in the pool, which will come into play later on. Arty goes over and reveals his secret, but Shelby freaks and lets him down with the "We're-from-two-different-worlds" speech. As if that weren't enough, the twins, who have been arguing atop the diving board, finally fall off, creating a huge splash that completely douses poor Carter. He stalks past Sam, who asks him casually how it went, though she's definitely trying not to laugh. Meanwhile, Austin's pals have completely come around to his way of thinking and have a surprise for him the CINDERELLA GAME (complete with dating-game type "Spanish Flea" theme). A few girls who look nothing like Sam come forward while Austin tells the boys, "You are so dead." The principal ends the game early, and we see Austin and Sam pass in the hall right before she hits her head on a locker while staring at him.
Back at Casa de Waters, Fiona is going through the mail when she sees something from Princeton for Sam. She opens it, and it's an acceptance letter with a course catalog and all the other stuff one would get in that kind of package. Her eyes widen and then Sam comes in and asks if she got any mail. Flustered, Fiona gives her something from Publishers Clearing House. Sam ignores it and heads upstairs. She sees some waiting messages from Austin begging her to tell him her name, and she sits down and slowly types My name is...
"SAM!" interrupts Gabriella. She tells Sam that her mom wants her downstairs, and Sam goes, leaving her computer on. Gabriella goes over to the computer, looks, and sees the messages from Austin, figuring out along with Brianna, who is sticking her head in the doorway that Sam is Cinderella. The next day the pair is at Mr. Ames's auto-place (though not with each other) where Austin is once again getting Mr. Ames' patented your-future-is-set speech, but this time with an added bonus, that being the info that a scout from USC will be there, and then his future really will be set in stone. He goes outside to wait on a customer, and it's Gabriella. She tells him that she's Cinderella, and then Brianna comes up saying that she's Cinderella. Austin, knowing better in both cases, says that his Cinderella lost something the night of the dance, and one who can correctly tell him what it was is his Cinderella. Brianna immediately says a wallet, and Austin smiles and says, "No." She laughs and changes her answer to a wallet purse, but still no. Gabriella blurts out, "A fish!" and Austin walks away as the two once again start fighting until they realize they've fought their way into a car wash which they come out of looking like Things One and Two from The Cat In The Hat.. Back at the house, Sam is in her room when Fiona comes in with a letter from Princeton. Sam tears it open and finds a rejection letter (written by Fiona, no doubt, but Sam doesn't know that). She starts crying and Fiona reassures her that she still has a job at the diner and offers her a cookie.
The next day, an undeterred and now incensed Gabriella and Brianna approach Shelby and tell her everything, and by everything, I mean they tell her that Sam conspired to break her and Austin up and created this whole Cinderella thing as a means to an end. That night, we see Sam getting an email from Austin asking her to meet him behind the bleachers after tomorrow's pep rally. Next we see Sam once again working at the diner (morning before the pep rally, presumably) when Austin comes in and sits down at the counter. She silently begs one of the other girls to take his order, but no dice she's gotta take it. She goes over and asks what she can get him, but he instead asks her what really gets him. "People taking your orders?" He says no, following orders does, and they start talking about how sometimes it's like you've gotta wear a mask. She almost gets to finally telling him the truth, but is interrupted by the arrival of Tweedledumb and Tweedledumber (Brianna and Gabriella). They knock a plastic Elvis guitar off the wall, tearing some wallpaper with it, and right then Fiona comes in. She asks what happened, and the girls blame Sam. Fiona tells Sam to pick this up and to clean the pool later, and that tears it for Sam she tells Fiona to shut up and that she quits her diner, her house, and most of all, her. This goes for pretty much everyone else in the diner, too, including one fat guy who takes his pie plate with him and says, "You can send me a bill." We later see her moving in with Rhonda, where she says she finally feels like she's home.
Next day is the pep rally. On the way there, Sam tells Carter everything that's happened on the way down there. The rally itself is much cheering and everything, and Mr. Ames is there to "support" his son. At some point, the cheerleaders start doing a little skit and it quickly becomes evident at least, to Sam, Carter, and Austin that it's really a slightly skewed version of what's been happening at school. The skit ends with Shelby proudly outing Sam as Cinderella, which makes Sam and Carter leave hurriedly. We later see Sam tossing aside her book of fairy tales, thinking that her dad was wrong and they don't come true after all.
The next day, everyone is laughing at the now-revealed Sam except for Carter and Austin, who doesn't know what to think. Shelby comes up behind Austin and tells him that people like Sam don't belong with people like them, but Austin doesn't say anything. Later, we see Sam rushing through the boys locker room looking for Austin and she tells him that she never pretended to be anything or anyone else, and that she knows there's a decent guy in him, but waiting for him to come out is like waiting for rain in this drought, impossible, but necessary, and she says if he comes out, she'll be there. She leaves and almost literally bumps into Carter. They talk, and he says that he's impressed over her telling off both Austin and Fiona. She asks what they should do, and he says they should go to the game. She agrees, reassuring him that she can handle it, and on the way there, she asks what character he's supposed to be today. He says, "Myself," to which she replies that it's his best look.
At the game, everyone but Sam is cheering, including Carter and Austin's dad, who is right down on the field. The game is played, and at the end of the fourth quarter with twenty-two seconds remaining, the score is thirteen to seventeen in favor of the other team. Austin starts heading out, but is stopped by his father who reminds him about the scout from USC. He doesn't say anything to this, but heads out to the huddle. As he's doing this, Sam says that she can't handle this after all and is going to leave. Austin looks at the stands and sees her gone, looks at the team, makes a choice and heads off field, tagging Dave on the way out and telling him that it's his game now. His dad stops him and tells him that he's throwing away his dream, but Austin just says, "No dad, I'm throwing away yours." He goes off field and blocks Sam on the way out, finally kissing her just as the rain finally starts, bringing the long drought to an end. Carter watches all of this unfold through the rain and says, "God, I love high school."
Now we hear Sam once again narrating. Seems that she was going through her fairy-tale book and found something, her dad's will. It left everything, the house, the diner, all of it to her in the event of his death. Next, we see Brianna and Gabriella going through some trashcans digging out Sam's acceptance letter to Princeton (Brianna finds it). We hear Sam say that after doing this, the twins put their teamwork to good use helping their mom work at the newly restored "Hal's Diner" under the watchful eye of Sam's business partner, Rhonda. As for Carter, he ended up getting a gig in a pimple-cream commercial and becoming respected in school, nabbing a girlfriend in the process, not his dream girl Shelby, but shock-jock DJ. As for Sam and Austin, they happily living together in their first semester together at Princeton at least for now, because as Sam says, she's only a freshman.