Upon release, Spy Kids received positive reviews from critics and became a commercial success by grossing over $147 million worldwide.
Carmen Cortez and her younger brother Juni Cortez live with their parents, Gregorio and Ingrid, whom they believe are boring, unaware that their parents are actually semi-retired international spies, working for an organization called the OSS (Organization of Super Spies, a reference to the Office of Strategic Services). Originally, Gregorio and Ingrid were enemies who were assigned to eliminate each other, but ended up falling in love and later got married. The two of them retired from the spy life prior to having children.
Carmen's main concern in life is with the unwelcome responsibility of babysitting Juni, and therefore she is usually mean to him. However, underneath her abusive exterior, Carmen is hiding secrets of her own: she skips school, and has to wear diapers at night due to having problems with bed wetting and in the day because she sometimes wets her pants and got a shot that sadly contained a small virus. She is desperate to keep both of these problems secret, especially from her brother. Juni lacks self-esteem and is a fan of a children's television show called "Floop's Fooglies." Hosted by Fegan Floop and co-starring the Fooglies—colorful, mutant, gibberish speaking friends of Floop—the show proves to be an irritant to Gregorio, who openly displays his dislike for the program. When he suspects the show is involved in the disappearance of several fellow spies, Gregorio and Ingrid decide to investigate and leave their children in the care of "Uncle" Felix Gumm, a man not actually their uncle but, rather, a family guardian. Gregorio and Ingrid are captured by Floop's men, Thumb-Thumbs, robots with thumbs for legs, arms and heads that wear red vests. Carmen and Juni discover the truth about their parents when they find that their parents have been kidnapped.
In Floop's island castle, the entertainer is reluctantly assisting a businessman named Mr. Lisp in creating an army of superstrong robots, using the children of world leaders as a disguise, to conquer the world. The robots were constructed by Floop's servant Alexander Minion. An item named the Third Brain is required to power the robots, or at least give them the ability to speak and think. Gregorio and Ingrid were brought in, due to Gregorio being one of the scientists who created the Third Brain and hid it, although he refuses to give the hiding place. Floop's minions invade the Cortez home, although Carmen and Juni escape while Felix is captured, but not before he tells the children the truth about their parents. The children flee to a safe house where they decide to become spies, until Ms. Gradenko, a fellow spy, arrives to help them. It is revealed that Third Brain is hidden in the house and that Gradenko is in allegiance with Lisp. The children escape but soon encounter robotic clones of themselves who steal the Third Brain and deliver it to Minion, who takes command of the robots and imprisons Floop in the Virtual Room where his show is usually filmed.
Carmen and Juni locate Gregorio's estranged older brother and inventor, Machete, who harbors bitter feelings against his younger brother, similar to the feelings Carmen harbored toward Juni; Machete was apparently forced to watch over Gregorio and left him because of this, and refuses to help the children. With no support from their uncle, the children sneak away to rescue their parents on their own, stealing a map of Floop's castle and a spy plane to get them there. Their sibling rivalry comes to a head, however, when Carmen's continuing criticisms and name-calling pushes Juni to retaliate by calling her "diaper lady," starting a quarrel that almost crashes the plane. As they work together to safely land the craft, Juni reveals that he had always been aware of Carmen's nighttime bedwetting, but kept that knowledge to himself at their mother's insistence. Having come to an understanding of each other as brother and sister, their relationship begins to improve from this point on.
The two make it to the castle and search for their parents. Juni finds Floop and frees him, convincing him to help them and explaining what was missing from his TV show- children. Carmen, Juni and Floop free Gregorio and Ingrid and then confront Minion, trapping him in a machine that creates the Fooglies on the children's show (who are actually the missing agents). Minion deliberately starts the machine but escapes before he becomes a Fooglie, altering his appearance with three extra heads and combined hands with multiple fingers. The spies confront Gradenko, Minion and Lisp and are confronted by their 500-man army of child robots. The family plots their next move while the evil trio marvels at the army, Gradenko looking the happiest of the three. When the family believes they need one more person, Machete arrives to help, later on claiming he came back for the same reason he left, meaning that he was told to watch over his brother. Just as Lisp orders the army to attack, Floop rewrites the children's minds to make them act like children. Despite Gradenko attempting to climb Lisp's chair for higher ground, she and her men are caught by the army. Gradenko and her fellow bad guys end up getting carelessly flung into the air with no regard for the well-being of Gradenko, Lisp and Minion, but this saves the Cortez family. Gregorio and Machete reform their brotherly relationship, with both of them claiming neither of them even remembering why Machete left, and Floop redesigns his show with Minion and the robotic Carmen and Juni as his new characters. The leader of the OSS, Devlin, offers the Cortez children jobs as spies, to which Carmen responds that the spywork is easy, while keeping their Cortez family together is the hardest mission of all. Having adopted a stronger value of family unity, she demands that they be allowed to work together as a family.
- Antonio Banderas as Gregorio Cortez
- Carla Gugino as Ingrid Cortez
- Alexa Vega as Carmen Cortez
- Daryl Sabara as Juni Cortez
- Danny Trejo as Isador "Machete" Cortez
- Cheech Marin as Felix Gumm
- Teri Hatcher as Ms. Gradenko
- Alan Cumming as Fegan Floop
- Tony Shalhoub as Alexander Minion
- Robert Patrick as Lisp
- George Clooney as Devlin
- Mike Judge as Donnagon Giggles / Donnamight