The boys disobey Dave and instead of seeing a kid's movie, they go in and see a horror movie. The movie ends up scaring the Chipmunks out of their wits. All night, the boys think that Hideous Harold, the creature from the horror film, is after them.

Theodore encounters a stray kitten that entered through an open window in the house. He and the boys take an instant liking to the kitten, and after some compromising, they name the kitten Cookie Chomper III, and after Dave is cured of his allergy to cats, he comes to like the kitten as well. After Cookie Chomper gets run over, the boys have a hard time dealing with it. Eventually, they get a new pet, a puppy they name Lilly.

The Chipettes are excited for the summer holidays, but not when Miss Miller keeps making other plans for them. The girls decide to hook her up with an elderly man by the name of Mr. Flowers.

Dave gets a bump on the head and forgets who he is. After seeing a commercial, Dave becomes a trendy stylish man.

Alvin is tired of being treated like a kid and trades place with Dave for a day to feel what it is like to be a grown-up.

The Chipmunks overhear Dave suggesting that he would prefer Alvin to be a Gymnastic Pizza Twirler, Simon a Pogo Stick Tester, and Theodore an iguana trainer, and immediately start to pursue those careers.

Alvin tampers with Simon's hair growth formula and instead having it grow Simon's hair, it turns him into a heartthrob.

Alvin is desperate to write an essay on George Washington, that he uses Simon's time machine to bring George into the future.

Alvin has a dream that he is a detective from the 40s. He is on a case to find a famous rich girl named Brittany.

Alvin lies to his classmates that he will be singing on stage with Michael Jackson. As Alvin tries to find Michael in order to see if it really is possible he could perform with him, he meets up with the big star's manager. To Alvin's surprise, this so-called manager is a homeless man looking to find a place to stay.

The Chipettes decide to quell Miss Miller's losing streak at poker with her girlfriends by secretly helping her cheat, which eventually leads her to Las Vegas, with the Chipettes in tow.

When the Chipettes are discovered to be living alone, Dave must find a supervisor for them.

Brittany attempts to market her own perfume.

The Chipettes discover the joys of writing in a diary. Tension builds between them when they deliberately sneak a peak at what the other Chipette has written.

Alvin becomes jealous when Simon becomes a celebrity in Australia.

Simon makes a video of his family for his class project. Unfortunately for Dave and his brothers he took the video in not their greatest moments, and is nervous when Simon’s video will air on TV.

Simon is frustrated being the smartest member of the family. He invents a cap that helps Dave and his brothers become smarter. Simon is so confident with his family’s new smarts that he signs them up to be on a genius game show. But before he could give his family another boost of the thinking cap, he loses it.

The Chipmunks encounter a scheduling conflict.

When the Chipettes are discovered to be living alone, Dave must find a supervisor for them.

The Chipmunks start a babysitting service, only to be bombarded with wall to wall babies.

The Chipmunks tell Dave's life story.

After Alvin, Simon and Theodore use Dave's antique gold pocket watch for Show & Tell at school, neighborhood bullies steal it. The Chipmunks find Mr.T to ask him for some advice and with his help they manage to get the watch back.

For the first time The Chipmunks meet their female counterparts, The Chipettes: Brittany, Jeanette and Eleanor.

A charaltan chipmunk named Harry claims to be Alvin, Simon and Theodore's long lost uncle and says he will have them see their mother as soon as they make enough money. The Chipmunks later not only find out that Harry is not their uncle but also the money he has them making is for a carnival strongman who he has owed for a long time.

The Chipmunks create a robot out of Alvin's video game, so that it can carry all of their equipment to their concerts. But, the robot goes beserk when it begins to capture every hat it sees, like the video game, it was created from, and It's up to Alvin, Simon, and Theodore to stop the robot.