About a family of seven monsters and their mother. Each monster is named after a different number from one to seven, and each has unique physical characteristics.
The Monsters learn the value of teamwork when they are sent to the store for milk. One wants to be in charge, Six falls asleep on the departing bus, Four tries to stage a mutiny and Seven loses his head. But, in the end, they pull together and bring home - Belinda the cow!
It is bedtime and the monsters will not listen to their Mom and go to sleep. Pillow fights, conga lines and even a mosquito hunt is among their antics. But when Mom reads them a fairy tale (featuring the Monsters in classic roles such as Cinderella, Snow White and Goldilocks) they tumble off to sleep.
Irascible Four must always look after his little twin brother Five. But, when Five's behavior includes eating Four's favorite toothpaste and polishing his ankles with Four's favorite toothbrush, Four does the unthinkable when he thinks Five isn't his brother anymore and blurts out that he wishes Five had never been born. Seven tells Four that he hurt Five's feelings. Mama crosses her arms and is very unhappy. Five thinks he's a bad boy and a good boy. When Five disappears, the Monsters think that Five has gone to the hospital to "Give himself back!" when it makes Four cry. The hunt is on when Four learns that an annoying Five is better than no Five at all. When he comes home crying, he wishes Five hasn't been his brother anymore, and One, Two, Three, Four, Six, and Seven begin to cry. So it's up to One, Two, Three, Four, Six, and Seven to get Five back.
A neighbor drops her baby off and the monsters decide to take up the challenge of babysitting. They then do their best to feed, change, entertain, and eventually go try to find the baby. Yes, they even lose the baby all without waking Mom who is getting some extra needed sleep. It's a lot of challenging work for the monsters.
One and Six have different ideas of how to stage their Mother's Day Party. Tempers flare and One suggests that if Six can't go along with her plan, maybe she'd be happier with another family. Six goes off in search of a "new" family, winding up as the star attraction at the circus.
For Two, there is nothing worse than waiting for a special package. He waits and waits and waits while the other monsters are having fun. Trying to be helpful, Seven searches for the package only to lose his head at the post office. The head travels around the world, but gets back home just in time to personally deliver Two's package.
With the help of "Doctor" Three, the Monsters try to cure Two's cold so they can all go to the movies. After many hilarious remedies lead nowhere, they discover that Mom's advice of getting plenty of rest is the best cure of all.
When a new girl named Mary moves in next door the monsters are eager to get to know their new friend, but the monsters all end up trying to outdo each other in impressing Mary because they each want to Mary to be their best friend. Mary discovers the monsters arguing and solves the problem by telling the monsters they can all be friends.
The monsters decide to buy a puppy but are unprepared as to how much work is put into owning one. In the process they forget about Belinda.
When the power goes out in their house during a storm, the Monsters find themselves scared. Four makes the matters worse by trying to spook the others only to find out he is the biggest 'fraidy cat' of all. Pulling together, they learn to be brave and that sharing their feelings is nothing to be afraid of.
When Four decides to be a movie director, he orders the rest of the monsters to make a video with him. But, after trying unsuccessfully to bully them into doing action, he learns that simply being nice gets more results.
With the big soccer game coming up, Seven feels like he's more of a burden to the team than some help. The other Monsters try and get him to be a better player, but in the end, it is Seven who teaches them all to work as a team.
When Five finds a wallet full of cash in the park, all the Monsters make plans for the money that isn't rightfully theirs. When they agree to wait a week for the real owner to come forward, sparks fly between the Monsters over the money. They have to learn the hard way that honesty is the best policy.
