After Alvin, Simon, and Theodore borrow Dave's antique gold pocket watch for Show and Tell at school, neighborhood bullies steal it.
The Chipmunks find Mr. T to ask him for advice and with his help, they manage to get the watch back. The Chipmunks meet Brittany, Jeanette, and Eleanor for the first time. However, there is one problem: A charlatan chipmunk named Harry claims to be the Chipmunks' 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 strongman whom he has owed money to 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 berserk when it begins to capture every hat it sees, like the video game it was created from, and it is up to the Chipmunks to stop the robot.
Alvin tells a girl, Julie, he wants Alvin and the chipmunks sploosh online dating impress that they are going to be starring in a rock concert on live TV, but Alvin must convince the producer to let them 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 them 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 monstrous Russian wrestler called Ivan the 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 UFOs.
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 Mother's Day 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 their choice wins.
Alvin decides to change the Chipmunks' clean-cut image to a punkier, more rebellious one in order to gain more publicity, but the trio ends up running from the Alvin and the chipmunks sploosh online dating when they attempt to perform in an underground club.
The Chipmunks make up a singing telegraph service to help buy some golf clubs for Dave's birthday. 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 college students who are bored. The boys enter a contest so that they can win a chance to sing with Dolly Alvin and the chipmunks sploosh online dating. But contest rules state only natives of Nashville, Tennessee are eligible.
The boys enter the contest anyway, but make an enemy when they win. Fiddlin' Freddie, a fiddle player who got second place in the contest, is determined to prove that the Chipmunks are not from Nashville, and win his chance to sing with Dolly Parton.
Dave has a nightmare of himself getting smaller and smaller.
Alvin is upset about his role as an angel in the school play. However, after a bump on the head, he believes he really IS an angel. It is now up to Simon and Theodore to make sure he does not mess up things TOO badly with his so-called "good deeds". 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
Alvin and the chipmunks sploosh online dating a ballet dancer, and when a bully begins to torment Alvin, he shows the bully 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 Alvin and the chipmunks sploosh online dating 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.
Hoping to get away from Shifty Jackson and his team of tabloid reporters, Dave drags the Chipmunks unwillingly on a camping trip in the great outdoors. When they finally arrive, the Chipmunks discover large footprints and think they are being followed by Bigfoot. Eventually they build a tree house for Dave, when he falls and injures himself badly, and Alvin and Simon go in search for Bigfoot. 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 animal fund and discovers that they do not have any money. In an attempt to earn some money, the boys decide to resell the cookies that Theodore bought with their money by dressing as Girl Cadets. When Theodore finds a dog, he feeds it all their cookies.
His brothers find out and decide to hide the dog from Dave. Simon later finds the dog's name is Pretty and that she belongs to an elderly man, Mr. Veevers, so the boys reunite Pretty with her owner. When the Chipmunks go to Hawaii, Alvin enters a surfing contest, and becomes convinced that he is cursed when he finds a medallion on the beach that is supposed 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 pickpocket 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. While on a train from Paris, the famed Orient Express, important papers are stolen and Alvin uses his recently acquired Official Top Secret Spy Manual to help solve the real-life mystery.
Alvin and a rich kid compete for a girl's affections. Alvin pretends he is as rich as his rival. Alvin, Simon and Theodore each make their own music videos for the group. The Chipmunks invest in an old broken-down horse to win a race. The Chipmunks compete against the Chipettes in a camp battle of the sexes. This time, he makes Alvin a movie star so he can break up the Chipmunks. So a hypnotist makes him have Alvin's personality, which turns out to be a disastrous move. The Chipmunks trick Dave to play golf with a man that Alvin made Alvin and the chipmunks sploosh online dating wager with.
What Dave does not realize is that Alvin bet his signed "Elmer Palmer" golf club.