Brittany was the first one born of the three Chipette triplets in Australia. All of them were orphaned, but it wasn't mentioned in the series. Luckily they we're taken in the care of by an orphaned human girl named Olivia in an orphanage, until they were kidnapped by Miss Grudge (the runner of the orphanage) and Eva (another orphan). The night when Olivia was adopted, they all escape to New York where they worked as miserable diner waitresses and lived on the streets. Until a few years later they moved to California and eventually hit the big time.
Brittany has, at times, been shown to be impulsive. However, she drives toward any goal she has set with complete determination, stopping just short of ruthlessness. During the series Brittany is depicted as domineering and as somewhat sarcastic and untrustworthy. An example of this is when she dismisses Simon's advice in The Chipmunk Adventure, when he advises them to avoid the easterly route to avoid Hurricane Arlene. She believes it to be a trick to slow them down so they'll lose the race. Also due to her ego, Brittany has been shown to be unable to admit her mistakes. Such as when her balloon is destroyed as a result of being caught in the hurricane. Her sisters demand that she admits her mistake, however as she is trying to admit it, she is unable to say the full sentence, instead changing the subject. However, Brittany is shown to be kind and compassionate, such as when she at first refuses to help Eleanor take home a kidnapped baby penguin but later submits after seeing its deep sadness and longing.
Brittany has been shown to be vain about her appearance. In the I Love the Chipmunks Valentine, it is shown that several boys wanted to go to the dance with her (although she only wanted Alvin) which means she is seen in boys' eyes as "attractive." Like Alvin, Brittany has always taken on the role as leader of the Chipettes, being lead singer or forward speaker for her sisters.
Brittany and Alvin have always shared an on/off relationship, often appearing to hate each other. However, they are known to express great feelings of love towards the other. The common scenario between the two is that at first they apear to be friends, but eventually butt heads, argue over the subject for a period of time (often blowing it out of proportion). Despite how bad things get, the two eventually agree that they care for the other and make up.
Though her basic concept is retained in the CGI films, there are some notable differences. Besides appearance, her personality is toned down. She is a lot friendlier and polite, making it easier for others to approach her. She is nicer and has better control over her temper than Alvin does, though it is still a bit shorter than most. She is also shown to have a much better, loving relationship with her sisters, becoming visibly concerned and defensive about them when her manager, Ian, tried to split them up. Unlike her cartoon version, she is able to apologize when she has judged wrongly. In Chipwrecked, her personality is a mixture of what she was like in the 80's and what she was like in The Squeakquel.