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.

When Four wins his brother Five a pet turtle at a fair Five and the turtle share a bond and become inseparable. Five even names the turtle Sam and goes as far as to give knit him a sweater, but during a bath time mishap Five thinks that Sam has gone down the bathtub drain. Five and his brothers and sisters explore the city drainage system to find Sam. When the reach the end of the line at the ocean they think that Sam has gone to his final reward. The family hold a memorial service and Five tries to deal with the loss. It isn't until they realize that Two is missing from the memorial service that they find out what really happened. Sam had fallen out the window and had climbed back in. Five and the others find him on Two's stomach. Two ended up with his nose stuck in the bath faucet and with no one to help him out he had simply fallen asleep.

One develops a lazy eye and must wear a patch over her good eye so that it can get better. What could be worse? She cannot fly, which she loves to do.

It's Mary's birthday and the monsters wanted to make the biggest surprise ever for her. However, Seven is fascinated with Monster Marbles after seeing a commercial for the product on TV. When the monsters go out to buy a present for Mary, Seven uses the money to buy the marbles. But soon, he decides to come clean and realizes that the marbles aren’t as great as they were advertised.

Six is mortified to learn before a big ballet recital she is losing a baby tooth. She tries to save the tooth with the help of her six siblings, but it's no use. She says that if she would be the swan than the ugly duckling. After Mom tells Six the story of the Tooth Dwarves, and when she lies down in bed, Six starts to cry first before Mom tells the story. Six learns everyone loses teeth and that the show must go on!

One just loves to play baseball with Billy. But why doesn't Billy notice? Six comes up with a plan to make One more of a girl but that doesn't seem to help anyone, especially the baseball team! After trying to play baseball in a dress, One realizes it's better (and safer) to be herself.

Two is lacking in confidence prior to appearing as a contestant on his favorite game show. But he learns that with experience and family support that he can achieve his goals by relying on himself.

An elephant named Wendy from the zoo follows Four home. Four decides to hide Wendy for good before the rest of the family sees him, because zoo animals are not allowed in the house.

Seven teaches everyone about fire safety after his lessons from Chief Lubomir. Number one: Always know how to detect smoke and gas. Number two: When fire is seen, get in an orderly line and walk to the nearest exit. Number three: Get in line and stay in the line in orderly fashion. Number four: Always remain calm. Number five: Don't go in unless the firefighter says it's safe to go back in. Then the monsters skills are put to the test when Two smells real smoke coming from the kitchen.

The monsters decided to travel around the world using a hot air balloon, but Mom is angry because she discovers that the monsters decided to make the hot air balloon out of their house.

Four helps Five prepare for a pie eating contest, but it ends up making Five and himself incredibly unhealthy and sick.

Four and Five learns a lesson about making practical jokes too far. They learned it after a pretend alien threatens to abduct them.

Four is frustrated with his brothers and sisters and wishes it were just him around and not them. His wish comes true, but very soon, he begins to miss them and regrets his wish.

The Monsters are charged with cleaning the basement, but they get a little distracted! They pretend they are living in a world of superheroes and villains and make a bigger mess than when they started. They learn that sometimes it isn't a good idea to get so carried away!