In 1995, a boy received a Buzz Lightyear toy inspired by his favorite film. This is the story behind that movie. A human spacecraft ventures in search of habitable planets located 4.3 million light years away from Earth. Upon detecting a potential planet, the craft awakens its commander from cryogenic slumber.
Buzz Lightyear, portrayed by Chris Evans, is a Space Ranger in Star Command. Alongside his commanding officer and close friend, Alisha Hawthorne (Uzo Aduba), they set out on an exploration of the habitable planet, T'Kani Prime, accompanied by their new recruit, Featheringhamstan (Bill Hader). Their mission takes a turn when they encounter hostile lifeforms, compelling the team to retreat back to their vessel. In the process, Buzz inadvertently damages the ship while ascending, resulting in a distressing need to evacuate for repairs. Tragically, the hyperspace crystal is destroyed.
Fast forward one year, the crew has established a fledgling colony, complete with essential repairs underway. They even manage to create a new hyperspace crystal, which requires testing before it can be put to use. Buzz, ever the volunteer, steps up to test the hyperspace fuel, a critical element for the repairs. His autopilot, I.V.A.N. (voiced by Mary McDonald-Lewis), aids him through the process. However, post a four-minute test, Buzz realizes that four years have elapsed on T'Kani Prime, a shocking consequence of time dilation caused by relativistic travel. This initial test is marked as a failure—due to the instability of the fuel, the ship was unable to reach hyperspace speeds. Buzz is resolute in his determination to perfect the fuel mixture to resume their mission.
As Buzz persists in his experiments, he is introduced to Sox (voiced by Peter Sohn), a robotic cat designed to provide companionship after his extended absence from the colony. To keep Sox occupied, Buzz assigns him the task of stabilizing the fuel. With each test conducted, four more years race by on T'Kani Prime, leading to an unforeseen total of 62 years of time lapse. During this extensive interval, the colony flourishes; Alisha forms a family with her wife Kiko, their son grows up, achieves a promotion, and eventually marries. Sadly, Alisha succumbs to old age, while Sox finally improves the fuel's composition, enabling it to reach faster-than-light speed.
Despite the new commanding officer Cal Burnside (Isiah Whitlock Jr.) advising against further hyperspace tests, Buzz feels compelled to act. Cal informs the crew that the colony has chosen to construct a laser shield as a defense against the hostile creatures, rendering the need for hyperspace exploration obsolete. Despite this, Buzz utilizes the newfound fuel mixture for a successful test of hyperspace travel. Unfortunately, the escape from the colony results in the loss of the computer containing the formula, leaving Buzz with a singular sample.
After landing, Buzz is stunned to learn that 22 years have passed. During this time, T'Kani Prime has fallen under attack from Zyclops robots, overseen by the enigmatic Zurg (voiced by James Brolin). Teaming up with defense force members, including Izzy Hawthorne (Keke Palmer), who is now Alisha's adult granddaughter, and the promising albeit naive recruit Mo Morrison (Taika Waititi), as well as the seasoned and elderly Darby Steel (Dale Soules), Buzz is initially hesitant but gradually accepts their assistance. Together, they devise a plan to infiltrate Zurg's ship and obliterate the invading forces.
Izzy leads Buzz to an abandoned storage area, where old ships are kept. As they attempt to escape giant creatures, Buzz commandeers a ship but finds himself chased by Zurg, who ambushes them and forces a crash landing on the planet's dark side. Following the attack, the ship's capacitor coil is damaged, and they must retrieve a new one from a nearby abandoned mine. Their plan is thwarted when Zurg tracks them down, uniquely focused on Buzz. Despite Buzz's escape, Zurg's robots manage to pilfer the hyperspace fuel.
In a climactic twist, Zurg captures Buzz and reveals himself to be an older version of Buzz from an alternate timeline. After successfully testing the hyperspace fuel, this alternate Buzz had been pursued by Burnside, which led him to escape and alter time significantly. With the help of time dilation, he adopted the identity of Zurg to acquire more fuel from his younger self, enabling him to traverse back and prevent the mission from ever occurring. However, Buzz firmly refuses to comply, recognizing the catastrophic consequences such actions would unleash, including the potential destruction of their timeline.
Meanwhile, Izzy, Mo, Darby, and Sox infiltrate Zurg's ship, leading to an intense confrontation where Buzz and his allies ultimately prevail, destroying Zurg's ship and escaping. Yet, Zurg survives the chaos and re-emerges, seizing the hyperspace fuel. In a consequential moment, Buzz shoots the fuel, igniting an explosion that incapacitates Zurg. With the fuel now gone, Buzz resolves to remain on T'Kani Prime. As he lands, Burnside attempts to apprehend Buzz but ultimately concedes, allowing him to reassemble the Space Ranger Corps. Buzz chooses Izzy, Mo, Darby, and Sox to be the fundamental members of this new team, much to Burnside's astonishment. The group embarks on a new adventure into the unknown.
In a post-credits scene, a seemingly lifeless Zurg drifts through space when suddenly, his eyes flicker to life.
