A crazed scientist sends out his mutant creations to kidnap young, beautiful men and women to bring back to his lab so he can transplant their brains into the bodies of old, wealthy people.
Leo, an egocentric, sexist businessman, who thinks he's God's gift to women, gets a taste of his own medicine when he tries picking up the wrong woman: a murderous psycho who shoots him. Leo falls off a bridge and emerges from the river, inexplicity transformed into a beautful woman. Naming herself Cleo, she (he) begins to place herself in Leo's life. While avoiding sexist office types and trying to find a way to turn herself back into a man, "Cleo" begins to develop her own personality that begins to take over Leo's.
Anna Coleman (Lindsay Lohan) is an average teenager with a stressful life due to her stodgy widow mother Tess (Jamie Lee Curtis) and annoying younger brother Harry (Ryan Malgarini). The conflicts revolve around: Tess' upcoming second marriage to Ryan (Mark Harmon), which Anna is not emotionally ready for because of her father's death three years ago; Anna's pop rock band Pink Slip, which Tess hates because according to Anna, she thinks that they are all noise; Anna's claims about her archrival Stacey Hinkhouse (Julie Gonzalo) who doesn't stop torturing her and has Tess convinced that she and Anna are still best friends like they used to be; and her sadistic English teacher, Mr. Elton Bates (Stephen Tobolowsky) who gives her an "F" on everything she does no matter how hard she tries. Tess also disapproves of Anna's crush, Jake (Chad Michael Murray), an older student.
The entire family, plus Ryan, eats out at Pei-Pei's Chinese restaurant, where Anna begs Tess to let her go on an important audition with the band. However, Tess refuses to let her go since the show is on the same Friday as the rehearsal dinner. The two begin arguing again until Pei-Pei's mother interrupts to give them fortune cookies, which contain a body switching spell, causing an earthquake only they felt. The next morning, Tess and Anna wake up in each other's bodies, figuring that the fortune cookies are responsible for the switch, but cannot go directly to the restaurant as Anna has to go to school and Tess has to attend to her therapy patients, taking each other's roles. At school, Tess finds that Anna is not only right about Stacey when she assaults her, but Mr. Bates also gives her an "F" on a pop quiz about Shakespeare's Hamlet even though she answered everything right. She soon recognizes him as a former classmate who asked her out to the prom, but she turned him down, and he is now taking it out on Anna. She threatens to report him to the school board unless he stops abusing Anna.
Before Anna goes to Tess' office, she gives Tess' body a makeover, much to her dismay. At lunch time, Anna and Tess go back to the restaurant to confront Pei-Pei and her mother, but Pei-Pei explains that only showing selfless love to one another will break the spell. In the afternoon, Anna attends Harry's parent-teacher conference, where she reads a composition about how much Harry actually admires Anna. She sees her brother in a different light and vows to treat him nicer. Meanwhile, Tess attempts to make amends with Stacey but she frames her for cheating. Jake helps her finish the test, which makes Tess realize that she has misjudged him. Unfortunately, Jake is no longer enamored with "Anna" after Tess sabotages Stacey's test.
Meanwhile, Ryan surprises Anna with an interview on a talk show to discuss Tess' new psychology book. However, Anna turns the interview into a wild romp to cover the fact she hasn't read the book. Tess and Jake catch the interview on TV and while Tess is embarrassed, Jake is impressed. Later, Anna bumps into Jake at a coffee shop and they bond over their favorite music. Jake begins to fall in love with "Tess" and attempts to pursue her, much to the real Tess' horror.
At the rehearsal dinner, Anna's bandmates come to try to convince "Anna" to sneak off to the audition but they are caught by security. Ryan surprises Tess and Anna by giving "Anna" permission to go. Ryan explains that he just wants the kids to accept him and Ryan urges "Tess" to go support the band, finally winning her over. Since Tess can't play, Anna unplugs her guitar and plays while Tess mimes along and enjoys doing so. Jake is in the audience and he realizes that Anna is the one for him. Tess also realizes how fun music is and promises to treat Anna's band with more respect. Back at the wedding rehearsal, Tess tells Anna to ask Ryan to postpone the wedding, so that Anna will not have to go through marrying him in her mother's body. Instead, Anna proposes a toast where she finally accepts Ryan because of how happy he makes Tess. This is the final act of selfless love needed to break the spell and another earthquake has the two switch back bodies. On the wedding day, Tess and Ryan marry, and Anna and Jake start dating with Tess' approval. Anna's band also plays at the wedding. Pei-Pei's mother attempts to give Harry and Grandpa Alan the body switching fortune cookies when they argue, but Pei-Pei confiscates them in the nick of time (by tackling them to the ground).
Woody Deane (Kevin Zegers) and Nell Bedworth (Samaire Armstrong) are neighbors and former childhood friends who go to the same high school, but are otherwise completely different. Woody is a popular varsity football player while Nell is a girl who loves literature but lacks social skills. They loathe each other and are constantly in dispute. One day their class goes on a school trip to a museum and they are forced to work together on an assignment. They quickly begin arguing in front of a statue of the ancient Aztecgod Tezcatlipoca.[5] As they argue, the statue casts a spell upon them — causing them to wake up in each other's bodies the next morning. When they arrive at school, they immediately blame each other for the body swap, but agree to pretend to be the other person until they can find a way to switch back. At first, they seem to succeed, but quickly return to arguing when they each feel the other is misrepresenting them in the opposite body, such as Woody (in Nell's body) answering a question oddly and surprising a teacher.
The following day, Nell (in Woody's body) arrives at school wearing "Chinos and an Oxford cotton button-down" making Woody's appearance look "dorky" which frustrates Woody, and he is even more frustrated after he hears about how Nell (in Woody's body) failed Woody's football practice the previous day. As payback, Woody (in Nell's body) dresses in inappropriate and provocative clothing the following day. After school, Nell (in Woody's body), in retaliation, breaks up with Breanna (Brooke D'Orsay), Woody's girlfriend, much to the disappointment of Woody. The humiliation competition continues when Woody (in Nell's body) drives off with a biker boy, Nicky (Brandon Carrera), and makes Nell (in Woody's body) think she is going to lose her virginity. However, Woody decides it is "so gay" and leaves Nicky just as he is removing his clothing.
The following day, rumors are being spread around school by Nicky about his night with Nell. When Nell (in Woody's body) finds out, she gets very upset. When Woody (in Nell's body) finds Nell (in Woody's body), he admits that he didn't actually lose Nell's virginity and that everyone was simply spreading Nicky's lies. However, Nell is still let down and so Woody (in Nell's body) decides to confront Nicky. It turns out that Woody (in Nell's body) can't fight him, and Nell (in Woody's body) runs up and punches him in the face. After this, Nell and Woody reach a truce and realize the statue of Tezcatlipoca at the museum had something to do with their body swap. They head down to the museum and even after confronting the statue, they fail to return to their original bodies. They realize they are going to have to help each other in two important upcoming events. Nell must learn how to play football for Woody's Homecoming game and Woody must learn about poetry and literature for Nell's Yale interview. Later that night Nell (in Woody's body) is getting drunk at a party while Woody (in Nell's body) is stuck at a slumber party listening to all the gossip about Woody, and surrounded by nailpolish, pajamas and slippers.
After spending so much time together, Nell and Woody become very fond of each other and start to understand each other better. The night before the interview and the game, they agree to go to the Homecoming Dance together, as "not a date." The day of the interview and match, Woody goes to Yale for the interview and at first messes things up and is asked to leave, but he starts to talk about poetry in rap, which impresses and astonishes the interviewer. After that, he goes to the match and watches Nell run in the winningtouchdown in the closing seconds. A college recruiter witnesses his good performance and wants to talk to him later. After the game, they congratulate each other for their successes. Shortly after this, the spell lifts and they return to their original bodies. The scene finishes with Woody being kissed by Breanna and Nell going home very upset about it.
The following day, Woody tries to talk to Nell but is stopped by her mother, who sees Woody's family as uneducated. Nell receives a letter from Yale informing her that she has been accepted to Yale, meaning that her interview (done by Woody in her body) was successful. However, she is still upset with Woody and has decided not to go to the Homecoming Dance. Meanwhile, Nell's father has a talk with her on the porch about Woody, during which she confesses she truly likes him, and her father surprises her with a dress and shoes for the dance. Woody and Breanna selected as the Home Coming King and Queen. The Home Coming King and Queen prepare to dance. At the dance, an upset Woody sees Nell and both confesses their love for each. They leave the school together and share a kiss in front of their houses. The following day, Nell tells her mother that she is taking a year's sabbatical before attending Yale, and hops into Woody's car as they drive off together.