Part 1: "Present"
The film begins at the start of a new school year, when Ron and his family move to Norway, and the villains Dr. Drakken, Shego, Duff Killigan, and Monkey Fist team up to steal the Time Monkey, a small statuette used to travel through time. With help from her computer guru Wade and her friend Monique, Kim follows the villains to Australia as they steal the body and head of the Tempus Simia, or "Time Monkey", but the villains connect the head to the body inside the Time Monkey's temple in Africa, and they escape through the resulting time portal.
Part 2: "Past"
Shortly afterward, Kim is visited by a large talking mole rat from the future, a descendent of Rufus named Rufus 3000, who gives Kim a time-travel device and explains that "The Supreme One" is preparing to take over the world. Meanwhile, Drakken uses a Juvinator on himself, Killigan, and Monkey Fist turn themselves into little children and travel back in time to Kim's first day in preschool in order to discourage her from becoming a crimefighter. Posing as her schoolmates, the villains try to bully the four-year-old Kim, but she defeats them and makes friends with Ron, and the high-school-age Kim arrives to fight Shego, who has been observing her accomplices.
With their preschool plot foiled, the villains turn back into adults and escape forward in time, to a day when Kim and Ron are middle-school teenagers. When a billionaire traps himself in the web of deadly laser beams that guard his vault, his security expert accidentally contacts Kim through her new baby-sitting website, so, after a neighbor drives Kim and Ron to the billionaire's mansion, Kim uses her cheerleading gymnastic skills to jump through the laser beams and save the billionaire. Monkey Fist goes into the past and retrieves a huge rock gorilla, which attacks Kim, but high-school-age Kim and Ron appear, and high-school Ron destroys the rock gorilla by accidentally activating the security lasers. As police officers arrest Drakken, Killigan, and Monkey Fist, Shego escapes with the Time Monkey into the future, where she will take over the world and become The Supreme One. High-school Kim and Ron follow her, along with Rufus and Rufus 3000.
Part 3: "Future"
In the future, Shego has become dictator of the world and made everyone her slaves. Kim and Ron are captured and sent to their old high school to be brainwashed, but they are rescued by Kim's twin brothers Tim and Jim, along with Rufus 3000 and an army of naked mole rats. The twins take Kim and Ron to the secret headquarters of the political resistance movement where they will be safe, whose leader is Wade, and Kim, Ron, Wade, the twins, and all of the Rufuses sneak into Shego's castle, where they fight their way past the villains and an army of monkeys to the room where Shego keeps the Time Monkey.
After capturing Kim and her friends, Shego explains that she separated Kim and Ron by making money in the 1990s stock-market boom, buying the company that Ron's mother worked for, and having her transferred to Norway. Keeping Kim and Ron apart enabled her to take over the world. In his anger at having to live in Norway and the destruction of his favorite nacho restaurant, Ron throws Drakken across the room. The twins break out of their chains, the pillars that hold up the palace ceiling collapse, and the Time Monkey falls to the floor and breaks, undoing all the effects of Shego's time travel. This causes Kim, Ron, and Rufus to float through a time portal and travel back to the first scene of the film, at the end of their first school day. At the moment when the first time disturbance occurred, a wave of time distortion washes over Kim and Ron, and when the moment has passed, the world has been restored to its original state and the two teens have lost all memory of the film's events, except that Ron knows he hates meat cakes, which he was forced to eat in Norway.
- Kim Possible: A Sitch in Time (movie version)
- Kim Possible: A Sitch in Time (movie version)
- Kim Possible: The Complete Second Season (episodic version)
- Christy Carlson Romano as Kimberly Ann "Kim" Possible, the titular protagonist.
- Dakota Fanning as Preschool Kim
- Will Friedle as Ronald "Ron" Stoppable, the deuteragonist
- Harrison Fahn as Preschool Ron
- Nancy Cartwright as Rufus, the tritagonist.
- Michael Dorn as Rufus 3000, a hyper-evolved futuristic descendent of Rufus.
- Tahj Mowry as Wade
- Michael Clarke Duncan as Adult Wade
- Nicole Sullivan as Shego, the hidden main antagonist. In the future, she rules the world.
- John DiMaggio as Dr. Drakken, the secondary antagonist. He becomes Shego's slave in the future.
- Tom Kane as Monkey Fist
- Brian George as Duff Killigan
- Gary Cole as Dr. James Timothy Possible
- Jean Smart as Dr. Ann Possible
- Shaun Fleming as Jim and Tim Possible
- Freddie Prinze Jr. as Adult Jim and Adult Tim Possible
- Raven-Symoné as Monique
- Vivica A. Fox as Adult Monique
- Kirsten Storms as Bonnie Rockwaller
- Kelly Ripa as Adult Bonnie Rockwaller, one of Shego's minions.
- In the serialized version, the scene where Ron asked Wade if he had a matter transporter is cut out.
- A running gag throughout this portion of the movie is Ron mistaking any non-English language for another.
- Every instance of Kim and Ron time traveling was accomplished by the scientific wrist device. Why would they be sucked into the magical portal at the end? It did not move then at any point.
- At the end, Kim and Ron are physically scooped up by the portal, yet do not physically arrive in the past, where they already were physically.
- When Kim is let out of the sarcophagus in the museum, her hair is messed up. When the camera comes back a moment later, her hair is perfect again.
- When Kim is looking in the Latin dictionary she is at "T" but she flips left and is at "S" when S is before T.
- As Kim and Ron pull apart from each other post-hug, Kim's hand goes through Ron's neck and Ron's hand goes through Kim's side.
- When preteen Kim finishes her try-out routine, Bonnie bites off part of her pencil. When you next see it, the pencil is whole.
- When the four villains open the time portal for the first time everyone walks through- in order- Monkey Fist, Shego and then Drakken. We never see Duff walk through, however he is later shown with all the villains as if he did so.
- Kim, in the pilot episode "Crush", in season one, saw Ron hold out Rufus after he found him in his pocket and asked Ron, when she saw Rufus: "A Naked Mole Rat?" like she didn't know all along that Ron had Rufus when Ron showed him to her, production wise, in their sophomore year, but in this episode Ron shows Rufus to Kim for the first time years before, while on a mission in the past.
- Though even before Kim said "A naked mole rat?" she showed that she knew about Rufus.
- It should be called into question how Rufus had descendants if he was lost in the time stream, as he wasn't shown to have left behind a child.
- Tempus Simia is said to be the Latin for "Time Monkey," but Latin cannot form descriptive terms merely by adding nouns in the same way English or German do, and "Tempus Simia" would mean something more like "Time is a monkey." Latin would require an adjective Temporalis Simia or a possessive Temporis Simia ("time-related monkey" or "monkey of time").
- Whenever Ron's parents have something big to tell him, they prefer to let actions speak for themselves. This is apparent throughout the series. In this episode, when asking about them moving, his father replied "The sign was our way of telling you". Another instance is when Ron is taken by surprise of his new baby sister in the episode Big Bother.
- It is possible Bonnie Rockwaller, Kim's archrival, may have been on the cheerleading squad longer than Kim, since she were the judges at the tryouts for the squad. If this is true, this may be why Bonnie feels that she should be the squad captain instead of Kim. And apparently when Kim had braces, Bonnie used to call her "Tin Teeth".
- Contrary to popular opinion, the girls with preteen Bonnie were not Tara and Hope. The blonde's hair and eyes are all wrong, as is the shape of the noirette's face.
- In the future, Ron falling to his knees in front of the destroyed Bueno Nacho is an allusion to the ending of the original Planet of the Apes when Charlton Heston's character did the same by the half-buried Statue of Liberty.