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.

Alvin is desperate to try and buy a Trans-Go-Go Bot, but Dave and his brothers will not lend him the money to get it. He decides to do the grown-up thing and get a job at the zoo.

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.

Simon hosts his own show, playing Sherlock Holmes investigating several mysterious robberies.

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 Chipettes are Alvie's Angels, a crime fighting team to hunt down the most popular jewel thief named Chazz Fleming.

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 tells a girl he wants to impress that they are famous and that they are going to be starring in a rock concert on live t.v., but Alvin must convince the producer to let him play.

Brittany tries to join the cool kids at school.

Alvin has a misunderstanding with a tough kid in his class, and ends up being challenged to a fight with him.

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

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.

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.

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.

While waiting for procrastinating Alvin on one of their dates, Brittany has a dream and becomes "Bratty Hayes" and Alvin becomes "David Alvinson", detective team. The plot revolves around Alvin trying to stop Brittany from marrying an evil villain - played by Simon.

Theodore develops a crush on a girl in his class named Juliet. Wanting some expert advice, Theodore asks Alvin for his help. Unwillingly, Alvin says a romantic line that Juliet overhears and she ends up developing a crush on Alvin instead of Theodore.

The origin of the Chipmunks is revealed, including how Dave ended up with the Chipmunks in the first place, as well as how their musical career got started.

Theodore goes on a diet so he could go on a date with a pen pal, who is also one of Alvin's biggest fans. Things go wrong when Alvin finds out that Theodore's date is actually the daughter of a famous film director. Alvin then takes her out instead, breaking Theodore's heart. In order for Alvin to make it to his play and the date, Alvin gets Theodore to switch back and forth to his play and on his date.

Brittany makes a bet with Missy Snootson, another girl in her class, that if the mummy of king Rooten Tooten does not rise from the dead and go to her home by midnight, Brittany must drop out of the race to be the school Carnival Queen.

After years of scrimping and saving, Dave is finally able to afford their own vacation cabin. Alvin hears that Robby Leach, the host of the show “Lifestyles of the Truly Fabulous” lives nearby. Alvin tries to get Leach to interview him, and at the same time he makes a few quick changes to Dave's cabin.

Dave meets a woman he really feels a strong connection with. At first the boys disagree, but finds she can get along with all of them. The only thing preventing this relationship to work is her own three boys clashing with the Chipmunks.

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.