On the run from their enemy, the so-called planet-destroying Gorg, an alien race known as the Boov find Earth a suitable place to call “home”. Led by Captain Smek (Steve Martin), they commence their “friendly” invasion of the planet, relocating the humans, whom the Boov deem as simple and backwards, to other parts of the planet while the Boov inhabit their homes in a quick and bloodless conquest. One of the Boov, named Oh (Jim Parsons), is a more excitable, freethinking member of the species, who decides to invite the Boov to his apartment for a housewarming party, despite the race’s antipathy towards him. Not far from Oh is a fourteen year old girl named Gratuity ‘Tip’ Tucci (Rihanna), who drives away through her home city to find her mother Lucy (Jennifer Lopez) after being separated from her during the invasion, leaving her with only her calico cat Pig and fueling her hatred for the Boov.
Oh runs into the street to meet up with a Boov cop named Kyle (Matt Jones), who, like the rest of the Boov, refuses to befriend him. Oh invites him to the party but accidentally sends a mass invite to every Boov on Earth. However, the “send all” button he pressed actually sends the invite to absolutely every alien race in the entire universe including the Gorg. Everyone, aggravated with Oh for revealing their location to the enemy, starts chasing him down. Oh runs into a convenience store to hide just as Tip and Pig enter the same store to grab supplies. They come across each other, and after Tip’s car fails to start, Oh transforms it into a fantastical, hovering craft to continue transportation. Oh hitches a ride with Tip when he promises to help her find Lucy, but unfortunately, they must to go to the Boov Command Center in Paris and locate her from there.
After reaching the Boov Command Center, which is in the now-floating Eiffel Tower, Oh manages to get into his account, and deletes the message with just a second to spare before it reaches the Gorg. He then plugs in Tip’s brain to help her find Lucy. They eventually trace her location to Australia, where she is also looking for her daughter. The other Boov then find the two and try to “erase” Oh, while Tip grabs the gravity manipulation system and flips it over, causing the whole Tower to tilt upside down.