The Chipmunks believe that Dave plans to propose to his new girlfriend in Miami.--and dump them. They have three days to get to him and save themselves not only from losing Dave but also from gaining a terrible stepbrother.
Alvin, Simon, Theodore have been living with, and annoying, Dave Seville for about 8 years now. Now they discover that Dave has a girlfriend and worry that he'll dump them for her. To save their relationship with Dave, the Chipmunks must find a way to stop him from proposing.
The (mis)adventures of Alvin, Simon, and Theodore continue with their manager/guardian Dave giving up songwriting to produce, so he can give them a more grounded life--but Alvin and the others love to perform. Dave has a new girlfriend, Samantha, whose son Miles treats them badly. Dave must go to Florida to help one of his artists, and he leaves the Chipmunks behind and takes Samantha. They think Dave plans to propose to her, and fear he'll ditch them. So they, along with Mitch, try to go to Florida to stop the proposal. But they don't have enough money, so the Chipmunks must ride in baggage, but when they're discovered, an air-marshal with a grudge against them decides to do away with them, so they force the plane to land. But they're far from Florida so they must go on foot.—[email protected]
Alvin, Simon, and Theodore, along with the Chipettes-- Brittany, Jeanette, and Eleanor--set up a surprise birthday bash for Dave that also serves as a good-luck party for the Chipettes, who are scheduled to be guest-judges on American Idol. Alvin invites and hires many people and celebrities to Simon's dismay before Dave returns home. The next day he takes them to mini-golf to meet his new girlfriend Samantha. The Chipmunks like her, but her son Miles is a bully who physically abuses them. Later, the Chipmunks find an engagement ring in a bag Dave brought home and believe he'll propose to Samantha, so they try to steal the ring.
A group of young celebrity chipmunks travel on a road trip to experience and see multiple new places. Along the way, they all discover that their lives and everything else could change dramatically. They try to figure out a way to stop the changes from happening.—RECB3
The movie begins with the Chipmunks and the Chipettes throwing a surprise birthday party for Dave, as well as being a good luck party for the Chipettes, who has been announced as judges on American Idol. Simon was rightly worried, because when Dave arrived home and saw the party he becomes furious.
Although still mad, Dave takes the munks to play mini golf, where they meet a doctor named Samantha. Dave and Samantha had been dating for a while. The munks go to play mini golf, however a boy named Miles physically abuses them and even attempts to sell Theodore. It is later revealed that Miles is Samanthas son. Later back at home, the munks find an engagement ring in one of Daves shopping bags and believe that Dave is going to propose to Samantha and worry about Miles being their new step-brother. Early the following morning they set out to steal the ring, to no avail.
Dave is going to Miami to produce a record for singer, Ashley Grey and he brings Samantha along as his plus 1. Miles is coming to stay with the Chipmunks and they all agree to go to Florida and stop Dave from proposing. Their next door neighbor Ms.Price was asked to keep an eye on the boys, but the munks hype up some squirrels and dress them in their clothes in an attempt to fool her.
Miles and the munks travel by plane, but cause a ruckus and Theodore travels in storage with a lot of other animals. Theodore lets out a monkey, who ultimately lets out the rest of the animals and the munks end up on the no-fly list, by James Suggs as revenge for the chipmunks causing his girlfriend to break up with him at Christmas.
Miles and the Chipmunks end up in a bar in Texas, where the munks perform, only to be caught by Suggs and they all take a cab, until they reveal they have no money and they are ditched at the side of the road. Miles admits that his father left him when he was younger and that is the reason he had been acting like a jerk. They busk in New Orleans, ultimately raising enough money for a bus fare. Unfortunately, the Mardi Gras parade was broadcast live on TV, which Dave sees and becomes so mad.
Dave and Samantha go to meet Miles and the munks at Louis Armstrong airport in New Orleans and ground them. Dave has to get back to Miami, but the munks are still on the no-fly list, so Dave has to drive them. In a hotel room, Alvin shows Theo, Simon and Miles that he had stolen the ring while no one was looking and the munks celebrate, but Miles seems disappointed.
To get over his disappointment, Miles goes for walk, with his headphones on and nearly gets hit by an oncoming car, but the Chipmunks slingshot Theodore into its path, saving Miles. The other munks revive Theodore with the scent of food and go to give back the ring. Suggs manages to catch up with the Chipmunks, but they trap him in an elevator. Miles and the munks arrive at the restaurant, where Dave and Samantha are having dinner, return the ring and announce that they would love for them to all be a family, only for Dave to say that it wasn't for him, but rather for his friend Barry who had proposed to his girlfriend with a breath mint. The Chipmunks grow even more guilty and decide to put on an apology concert for Dave.
The Chipmunks and Ashley perform an apology song titled, "You are my home" and they invite Barry to re-propose to his girlfriend, successfully this time. On the way home, Dave takes the Chipmunks to the courthouse to officially adopt them. They return to the house for the first time as a legal and official family, only to find that the drugged up Squirrels have completely ruined the place, which greatly annoys Dave. In the end credits, Suggs is freed from the elevator and relaxes by the pool and refuses to leave, so two security guards carry him out.
