Little Monsters is a 1989 comedy film starring Fred Savage as Brian Stevenson, a sixth-grader who has recently moved to a new town, and Howie Mandel as Maurice, the monster under the bed.
The story purports to explain "what really goes on under the bed" and why children are always getting blamed for things they did not do. Beginning as a flashback, it tells of how Maurice befriends Brian and shows him a world where there are no rules and no parents to tell them what to do. However, there is more to this fantasy world than meets the eye, and when Brian's brother Eric (Fred Savage's real life brother Ben Savage) is kidnapped, the fun and games turn deadly serious.
Lonely after moving away from friends, Brian finds himself blamed for several things he apparently has not done. A quart of ice cream is left in the cupboard, Brian's bike is left on the driveway (causing his father to crash into it on his way to work). Brian insists he is innocent and blames his brother, Eric, who claims to have seen a monster the night before. As revenge, Brian snatches Eric's lunch and tosses it out the window, hitting Ronnie Coleman, the school bully who boards the bus and antagonizes Brian.
That night, while sleeping in Eric's room for a bet, Brian hears a loud noise, the source of which quickly disappears under Eric's bed. The next night, a determined Brian sets booby traps and captures the intruder: a blue-skinned monster named Maurice. Though scared at first, Brian soon discovers that he and Maurice share the same interests and befriends him. Over the course of several nights, Maurice shows him a fun time in the monster world beneath Eric's bed. It consists of every child's dream: all the junk food and video games they want, and no adults to tell them what to do. It also has innumerable staircases leading to the spaces beneath children's beds, from which the monsters cause trouble. Maurice and Brian have fun making mischief in other people's homes, and Brian feels he has found a true friend at last – although Brian seems to be changing. He learns that he is turning into a monster, as his body parts shrink when the light hits him.
This changes Brian's mind about Maurice and he saws off the legs of all the beds in the house. Due to Maurice's failure to convert Brian (all monsters are former children), Eric is kidnapped by Snik (another monster) through the couch bed in the living room. Brian enlists the help of his friends, Todd, Kiersten, and Ronnie. Gathering an assortment of bright lights, they enter the monster universe in search of Eric. "Zapping" various monsters along the way, they march to the master staircase, where Boy, the ruler of the monster world, resides. Boy offers to let Eric go if Brian agrees to convert, but Brian refuses. The bright lights are destroyed and they are all placed with Maurice in a locked room. They manage to escape by turning Maurice into a pile of clothes (via an improvised light) and slide him through the door crack. They re-arm themselves with more powerful light and destroy Boy, explode Snik (who later puts himself together), and rescue Eric.
The kids appear to have lost until Maurice appears with a flamethrower. He sets Snik ablaze, allowing Brian and the others to escape. Unfortunately, they find that they cannot return home because the sun has risen. Faced with the prospect of turning into monsters if they do not return to the human world by sunrise, the children travel in the monster world from the Atlantic time zone to Malibu where the sun has not risen yet and they manage to escape. Brian and Maurice share a heartfelt goodbye, and Maurice gives Brian his bomber jacket to remember him by, as the kids play in the beach. Brian inside a telephone booth calls his parents, and tells them that Eric is fine and that they're in Malibu. When his parents ask why they're in Malibu, Brian responds that it's a long story. The movie ends in a freeze frame of Brian, still on the phone with his parents.