While on a road trip, a family stops at a rest stop where they encounter a man being pursued by small, furry, and ferocious creatures known as Critters. The creatures, who have escaped from a previous confrontation, stow away on the family's car as they continue on their journey. Unbeknownst to the family, the creatures are alien fugitives that can roll into balls, shoot poison quills, and have an insatiable hunger. As the family arrives in their Los Angeles apartment building, they are unaware that they have brought along these dangerous passengers.

Soon, the Critters begin to infest the apartment building, causing chaos and terror among the residents. The tenants, a quirky and diverse group, must come together to fend off the Critter invasion. As the creatures multiply and their attacks become more ferocious, the family and their neighbors find themselves fighting not just for their lives, but for the safety of their community. Amidst this battle, friendships are formed and the residents realize that they must rely on each other to survive the onslaught.