On the run from their formidable enemy, the planet-destroying Gorg, the Boov—known as the best species ever at fleeing—discover Earth to be a perfect place for them to establish their new "home." Under the leadership of Captain Smek (played by Steve Martin), the Boov initiate their so-called "friendly" invasion. Their strategy involves relocating humans by temporarily reversing Earth's gravity and using enormous vacuums to extract people from their homes. This unsettling operation leads to the Boov categorizing humans as simple and backward, and they move them to designated areas such as a massive colony in Australia dubbed Humanstown, while the Boov settle into the vacated homes with astonishing speed and minimal conflict.
Among the Boov is a unique member named Oh, portrayed by Jim Parsons, who is characterized by his enthusiastic and free-thinking nature. Unlike his fellow Boov, Oh invites his brethren to a housewarming party in his apartment, despite their typical disdain for individuality. A notable aspect of the Boov is their extraordinary ability to change colors depending on their emotional states.
Meanwhile, not far from Oh, a young human girl named Tip, played by Rihanna, is desperately making her way through her city after getting separated from her mother, Lucy (portrayed by Jennifer Lopez), during the invasion. All she has left is her calico cat, Pig, and a growing resentment toward the Boov race. As fate would have it, Oh accidentally crosses paths with the rebellious Tip and her cat while trying to hide from a Boov cop named Kyle, played by Matt Jones. Despite their initial conflict—Tip's anger towards Oh for taking over her planet and separating her from her mother—circumstances force the two to join forces. Oh, despite lacking knowledge about handling a hovering vehicle, manages to transform Tip's non-functional car into a fantastical mode of transportation running on Slushies, aptly named Slushious, and pledges to assist Tip in her quest to find Lucy.
Their adventure leads them to the Boov Command Center located in an upside-down Eiffel Tower in Paris, where Oh must contend with Captain Smek, who is attempting to delete an intergalactic party invite Oh inadvertently sent to all alien races, including the Gorg, which puts them on a tight timeline of 40 hours. Oh's peculiar password thwarts Smek's cancellation efforts, causing significant chaos.
As they navigate through the dangers, including close encounters with the relentless Gorg ship headed their way, Oh learns more about human emotions and family bonds, realizing that Tip deeply misses her mother and that in the Boov world, there are no mothers. Fulfilling his promise, Oh helps Tip locate Lucy, but tensions rise as Oh hesitates to reunite with the Boov during the final evacuation.
Heartbroken and hurt from the lies, Tip eventually tracks down her mother with Oh’s help, culminating in a heartfelt reunion. With the Gorg mothership looming closer, Oh heroically steps up, drawing the Gorg's attention by revealing the stolen Shusher rock with its hidden treasure of Gorg larvae—signifying the survival of the Gorg species. In a surprising twist, the Gorg Commander, initially perceived as a villain, turns out to be a gentle creature.
In the aftermath, two weeks later, harmony is restored as humans return to their homes, and Oh successfully throws his long-awaited party, inviting both humans and Boov to celebrate together. As music fills the air, the Boov experience dancing for the first time, marking a new beginning for relationships among species and a hope for peaceful coexistence. The party gains an unexpected audience as ships from other planets, including the Gorg, arrive, responding to Oh's invitation, solidifying a joyful chapter for all involved.
