The origin of the Chipmunks was totally rebooted in 2007 for its feature film. They are living in a tree, fending for themselves as their parents had taken off to join a hippie commune, and having problems gathering nuts for the winter. Their tree is cut down and carted off to grace the entrance lobby of a city office building, with them in it. They then hitch a ride in a basket of pastries Dave is carrying and wind up in his home, where they wreak havoc & uproar in his kitchen and get thrown out before showing Dave how well they can sing and becoming celebrities as a result. Despite repeatedly testing Dave's putting up with them, they finally win his heart.
Alvin is the lead vocalist and is the middle of the Chipmunks. He wears a red baseball cap and sweater sporting a yellow "A". His eyes are blue (amber in the live action/animated films) and his build is thin. In personality, Alvin is enthusiastic, mischievous, wacky, hot-tempered, and funny. The term look before you leap does not usually apply to Alvin, as he is impulsive, charming and musically talented. He often makes up harebrained schemes to achieve his goals, whether it be trying to help his brothers, keeping Dave from figuring something out, or getting out of a sticky situation. Alvin seems to refer to his often illogical or crazy plans as "challenging the ordinary". He is proud of his fame and often self-centered and vain, but Alvin does have a kind heart and loves his brothers very much, often proving that his heart is stronger than his voice. He's also not ashamed to admit when he's wrong and will help others when the time comes. There are times when Alvin displays true selflessness, such as when he gave his golden harmonica to a sick boy at Christmas and when he helped Theodore get Nathan, a bully, off his back for a while.
He is shown to be infatuated with Brittany, although they often quarrel with each other, but they look out for each other when things look bad. He sometimes struggles with her to prove who is the better, such as when he and Brittany each ran for class president at their school in the animated series, but he is often kind to her and is implied to have a crush on her. He sometimes displays affection for Brittany such as hugging her, kissing her hand or cheeks, and comforting her when she is upset. In one CGI episode, Alvin heard two girls insulting Brittany and he stood up for her, displaying his gentle side once again.
Like his brothers, Alvin was originally voiced by Ross Bagdasarian Sr. In the animated series and film, he was voiced by Ross Bagdasarian Jr. Justin Long voiced Alvin in the live-action/animated film series. On July 30, 2002, Alvin was No. 44 on TV Guide's list of "Top 50 Best Cartoon Characters of All Time".
Simon is the eldest brother and the tallest of the Chipmunks. In addition to having an IQ just north of Einstein, Simon possesses a dry sense of humor as well as keen wit. He wears glasses and blue attire, and has blue eyes (a trait he shares with Alvin). He is kind, gentle, logical, responsible, and at times poetic. He often takes charge when Alvin goes too far with his harebrained schemes. Although Simon tends to disagree and argue with Alvin, he truly loves his brother and sticks by him despite everything. Simon tends to hold grudges, but these are often short-lived as he knows that he should be more forgiving. Simon plays the bass, bass clarinet, saxophone, bagpipes, tuba, and drums, among others. In vocal harmonies, he consistently sings the lower parts due to having a deeper voice than his brothers. He is shown playing the keyboard in the original open for the 1980s series. He was also shown playing guitar in a 1980s Hardee's commercial.
Simon is often implied to have a crush on Jeanette, as she is like him in many details; wearing glasses and blue or purple attire and having a high IQ, possibly rivalling his own. However, he seems braver in standing up to siblings than her because Jeanette doesn't often stand up for herself when Brittany pushes her around. But like Simon to Alvin, Jeanette shares a sisterly bond with Brittany.
Like his brothers, Simon was originally voiced by Ross Bagdasarian Sr. In the animated series and film, he was voiced by Ross Bagdasarian Jr. Matthew Gray Gubler voiced Simon in the live-action/animated film series.
Theodore is the child of innocence and the youngest of the Chipmunks. He is shy, loving, sensitive, chubby, gullible, trusting, and naïve. In short, he is an easy target for Alvin's manipulations. He wears green attire and has green eyes (brown in the CGI animated series). Theodore often holds the swing vote between his two brothers' choices of action. Simon appeals to Theodore's better nature while Alvin goes straight to bribery. He has a big appetite, constantly craving snacks and in one episode, Theodore tried to eat Alvin's hand because of his hunger. He plays the drums, the guitar, and other instruments. In vocal harmonies, his voice is typically the highest. He is fragile yet unpredictable and not very brave, but he will put on a brave face when his brothers are in trouble. At times, he is childish and Alvin's follower, but he is also the glue that binds his brothers despite Alvin and Simon's differences and regular disagreements. Although he is sometimes teased by Alvin, Theodore loves his big brother and knows that Alvin loves him too.
He seems to have affection for Eleanor, who shares physical traits with him, but she is smarter, braver and more athletic. They each have a passion for cooking, as Theodore is seen baking Christmas cookies in some Christmas episodes. In the live action/animated films, it is revealed that Theodore is sensitive about his weight and is often hurt when he is criticized for his chubby physique. This also applies to Eleanor, but she is able to stand for herself and wishes that Theodore would do the same.
Like his brothers, he was originally voiced by Ross Bagdasarian Sr. In the animated series and film, his voice was provided by Janice Karman, Ross Bagdasarian Jr.'s wife and the voice of all three Chipettes. Jesse McCartney voiced Theodore in the live-action/animated film series.