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.
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.
Alvin unknowingly assists a jewel thief steal some jewelry from a cabin on their cruise ship, and Simon and Theodore begin to investigate the crime.
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.
Alvin and Simon have Theodore enter a wrestling exhibition under the name "Mr.Fabulous" and he goes up against a montrous Russian wrestler called Ivan The Terrible.
The Chipmunks meet their grandparents for the first time. Then, when they discover that someone is trying to take over their Grandparents farm, they decide to raise the money needed to save the farm.
Alvin convinces Theodore to dress up as an alien to attract more fans, but they also attract some investigators with the government who research ufo's. The investigators decide to kidnap Theodore and perform experiments on him and Alvin and Simon must think of a way to save him.
Alvin, Simon, and Theodore go in search for a mother to attend their school picnic. Each choose the person, that they each think Dave will like best. But, when all three of their choices arrive at their house, Alvin, Simon, and Theodore, will do anything to make sure that their choice wins.
Alvin decided to change the Chipmunks image to gain more publicity, but end up running from the police, when they attend a rave.
The Chipmunks make up a singing telegraph service to help buy some golf clubs for Dave's Birthday. But when Theodore loses the addresses, the boys are sent on a birthday mission, for a 100 dollar bonus. Except, that when Theodore wrote the number he wrote it upside down, so the Chipmunks end up going to the wrong house and are tricked into doing some different pranks for some highschoolers who are bored.
The boys enter a contest so that they can win a chance to sing with Dolly Parton. But, the only way they can win is if they are from Nashville. The boys enter the contest anyway, but make an enemy when they win. The person who got second place in the drawing is determined to prove that the Chipmunks aren't from Nashville, and win his chance to sing with Dolly Parton.
Dave has a nightmare of himself getting smaller and smaller.
Alvin loses his memory and thinks that he is an angel.
Dave hires a nanny to take care of the Chipmunks when he is away at work, and the Chipmunks will do anything to get rid of her.
The Chipmunks invite a boy to stay with them who is a ballet dancer, and when a bulley begins to torment Alvin, he shows the bulley that ballet is cool.
Alvin demands a short trip away from obsessed fans who begin following him everywhere he goes. So, the Chipmunks go for a picnic out in the woods, only to be found again by their fans. Alvin runs off into the woods, and runs into a wild chipmunk. He decides to change places with the chipmunk, and he stays in the chipmunk's tree, while the wild chipmunk takes his place. All goes well until the real Alvin is caught by a hunter that holds him hostage. Simon, Theodore, and the wild chipmunk must save Alvin before it's to late.
Dave drags the Chipmunks unwillingly on a camping trip in the great out doors. When they finally arrive, the Chipmunks discover large footprints and think they are being followed by Bigfoot. Eventually they build a treehouse for Dave, when he falls and injures himself badly, and Alvin and Simon go in search for Big Foot.
Charlatan chipmunk Harry returns and this time pretends to be Santa Claus and cons Alvin, Simon and Theodore into building a Christmas-themed amusement park called "Santa's Place".
Alvin donates money to an animalfund raiser, and discovers that they don't have any money. In, an attempt toearn some money, they decide to sell the cookies that Theodore spent their, money on. But, when the Chipmunks find a dog, they must hide it from Dave.
When the Chipmunks go to Hawaii, Alvin enters a surfing contest, and becomes convinced that he is cursed when he finds a medallian on the beach that is suppose to bring bad luck.
The Chipmunks get a job as vendors at a baseball stadium, to pay for new uniforms for their baseball team. And in the process stop a pick pocket who has been stealing money.
The chipettes move to the Chipmunks school and Alvin and Brittany run against each other for class president. Both will stop at nothing to win, but when the polls are revealed they discover that Jeanette has the deciding vote.