Julius Benedict (Arnold Schwarzenegger) and Vincent Benedict (Danny DeVito) are fraternal twins, the results of a secret experiment carried out at a genetics laboratory to produce the perfect child. To the surprise of the scientists, the embryo split and twins were born. The mother, Mary Ann Benedict, was told that Julius died at birth, and not told about Vincent at all. Julius was informed that his mother died in childbirth. Vincent believed his mother abandoned him. Each twin is unaware of the other's existence.
Jerry Shaw (Shia LaBeouf) is a Stanford University dropout who learns his identical twin brother Ethan, a first lieutenant in the US Air Force, has been killed. Following the funeral, Jerry is surprised to find $750,000 in his bank account. Later he finds his Chicago apartment filled with weapons, ammonium nitrate, classified DOD documents, and forged passports. He receives a phone call from a woman (Julianne Moore) who warns that the FBI is about to arrest him and he needs to run.
Recently divorced Helen Grace (Mary-Louise Parker) moves into the Spiderwick Estate with her children when it is given to her by her elderly aunt Lucinda (Joan Plowright), though identical twins Jared and Simon (Freddie Highmore) and their older sister Mallory (Sarah Bolger) do not want to move from the city. When Jared uncovers a dumbwaiter system behind a wall, Jared finds a monogrammed key and discovers the study of the late owner of the estate, Arthur Spiderwick (David Strathairn). Jared uses the key to open a chest. In it, he finds Spiderwick's field guide to faeries; although an attached note warns him not to read it, he does so anyway.
The film begins with a magician (Michael Caine) performing a vanishing bird illusion for a young girl explaining that each trick has three parts: The Pledge, where the audience is presented with an ordinary object; The Turn, where the object is turned into something extraordinary; and The Prestige, where the object is brought back.
Dan Rayburn (Robin Williams) and Charlie Reed (John Travolta) are best friends and co-owners of a successful sports marketing firm. Seven years prior, Dan, recently divorced, married Vicki (Kelly Preston) after being whisked away by Charlie for a tropical vacation. The wedding, however, is short lived. Seven years later, Vicki resurfaces to tell Dan that their short marriage resulted in something he never suspected: twins Zach (Conner Rayburn) and Emily (Ella Bleu Travolta).
In 1986, Nick Parker (Dennis Quaid) and Elizabeth James (Natasha Richardson) meet and get married during an ocean cruise on the RMS Queen Elizabeth II. After the birth of their twin daughters, Annie and Hallie (Lindsay Lohan), Nick and Elizabeth divorce and lose contact, each parent raising one of the twins without telling her about her sister. Nick raises Hallie in Napa Valley and becomes a wealthy wine grower, while Elizabeth raises Annie in London and becomes a famous and wealthy wedding gown designer.
Organization of Super Spies (OSS) agent Marissa Wilson (Jessica Alba) is leading a team of agents attempting to capture a criminal named Tick Tock (Jeremy Piven), who purchases a mini-disk stolen from OSS. Despite being nine months pregnant and going into labor, she continues her pursuit, against the admonitions of her boss, Danger D'Amo (also played by Jeremy Piven). Tick Tock is captured and the mini-disk, which contains information on a weapon of mass destruction called Project: Armageddon, is retrieved.
Washington, D.C. detective and forensic psychologist Alex Cross (Morgan Freeman) heads to Durham, North Carolina when his niece Naomi (Gina Ravera), a college student, is reported missing. He learns from the local police, including Detective Nick Ruskin (Cary Elwes), that Naomi is the latest in a series of young women who have vanished. Soon after his arrival, one of the missing women is found dead, bound to a tree in a desolate forest, and shortly after that, intern Kate McTiernan (Ashley Judd) is kidnapped from her home.
Identical twins Susan Evers and Sharon McKendrick meet at summer camp, unaware that they are sisters. Their identical appearance initially creates rivalry, and they continuously pull pranks on each other, which ultimately leads to the camp dance being crashed by their mischief. As punishment, they must live together in an isolated cabin (and eat together at an "isolation table") for the remainder of their time at summer camp. After both admit they come from broken homes, they soon realize they are twin sisters and that their parents, Mitch and Maggie, divorced shortly after their birth, with each parent having custody of one of them. The twins, each eager to meet the parent she never knew, switch places. They drill each other on the other's behavior and lives, and Susan cuts Sharon's hair into the same style as hers. While Susan is in Boston masquerading as Sharon, Sharon goes to California pretending to be Susan.
17-year-old sisters Jane (Ashley Olsen) and Roxy Ryan (Mary-Kate Olsen) are completely different and never see eye to eye, and live with their father in a suburban Long Island neighbourhood. Over a 24-hour period, the two begrudgingly journey together into the city for Jane, an uptight overachiever, to deliver a speech to qualify for a prestigious college scholarship abroad, and for Roxy, a laid-back punk-rock rebel, to get backstage at a music video shoot so that she can give her demo tape to the group.
The movie centers upon the brother and sister pair Tony and Tia, whose surname they initially know only as that of their deceased adoptive parents, Malone. The children are placed in an orphanage, where they face difficulties stemming from their strange psychic/psionic abilities: Tony can psychokinetically move and control inanimate objects with the aid of his harmonica, while Tia can communicate telepathically to Tony, commune empathically with animals, and experience premonitions. Tia also possesses minor telekinetic abilities. She carries a "star case" with her at all times, which eventually reveals a strange map.
Two unrelated young girls who happen to look identical suddenly meet. Amanda Lemmon (Mary-Kate Olsen) is an orphan, and she is about to be adopted by the Butkises, a family whom she doesn't like. She actually wants her child-loving social worker, Diane Barrows (Kirstie Alley), to adopt her instead. Diane would like to do so, but authorities will not let her because of her low salary. Alyssa Callaway (Ashley Olsen) is coming home from her boarding school's piano recital competition, only to find that her wealthy father, Roger (Steve Guttenberg), is about to marry Clarice Kensington (Jane Sibbett) a socialite who threatens to send her soon-to-be stepdaughter to boarding school in Tibet.
Having spent a good deal of time enjoying the company of their newfound family and friends at Witch Mountain and intensively studying and practicing their supernatural powers, Tony and his sister Tia are in need of a vacation. Uncle Bené drops them off in their flying saucer at the Rose Bowl stadium in Los Angeles, California, after which the siblings quickly become separated from each other. A man named Dr. Victor Gannon (Lee) and his assistant Letha Wedge (Davis) happen to see Tony using his powers to save their henchman from certain death. Realizing that Tony has supernatural powers, Dr. Gannon drugs the boy with a tranquilizer shot and takes him back to their laboratory. There, Dr. Gannon successfully tests a new mind-control technology on him. Under its influence, Tony is completely hypnotized and does everything that his kidnappers want him to do, like stealing gold from a museum exhibit and stopping Tia from finding them. With Tony at his robotic bidding, Dr. Gannon hopes to achieve recognition within the scientific community and worldwide power, while Letha merely wants a return on her investment.
Pim was born as a twin, conjoined at the stomach with her sister, Ploy. Pim was very sweet and protective of Ploy. However, it was Ploy who threw rocks at a group of children who were taunting them. Pim and Ploy always promised each other to stay together till the end of their lives.