Tanya Mousekewitz is the eldest child of Mama and Papa Mousekewitz and the older sister of Fievel and Yasha. She is a cheerful, optimistic, beautiful, cute, obedient and energetic young mouse who is famous for having faith that Fievel was alive when her parents refused to believe it in An American Tail. She looks and acts a little different in every sequel; in Fievel Goes West she is shy and wants to be a singer, in The Treasure of Manhattan Island she is spunky and sarcastic, and in The Mystery of the Night Monster she is also spunky and sarcastic but has a deep crush on newspaper editor Reed Daley.
In An American Tail, she wears a red babuska (headscarf), a blue blouse with a navy jumper dress and frilly white bloomers underneath. She was also much closer to Fievel's age. She looks much the same as this in The Treasure of Manhattan Island (pictured). In The Mystery of the Night Monster she looks taller than in the last movie, and her hair is very short. She has stopped wearing her babushka and insteads wears a slimmer, professional-looking white blouse and purple skirt.
In An American Tail: Fievel Goes West, she was much older likely in her early teens and her age range from Fievel was increased. This was her oldest incarnation, as in later sequels she is aged down again. She dropped her red babuska for a long ponytail and an orange and brown dress. She had big aspirations to become a singer and had a beautiful singing voice, which did "fit in" well with her New York neighbors (as Mama Mousekewitz prepared some of the food they throw as the family dinner).
An American Tail
In the first film, Tanya gets a babushka for Hannukah while Fievel gets his hat. She has her doubts about leaving Russia after the cat attack, but goes along with her family to America anyway. She is as hard hit as the rest of her family by Fievel's apparent death but she never loses hope that he survived falling off the ship somehow. She sang the heartwarming but distant duet "Somewhere Out There" with her brother Fievel when they were separated. Whenever Tanya begs her father to look for Fievel, it turns out Fievel is nearby but they don't see each other. She's finally proven right late in the film, when the Mousekewitz's meet Tony and Bridget. She's last seen riding on Henri's back with Fievel at the end of the film as they check out the newly built Statue of Liberty.
Fievel Goes West
At the beginning of the film it is shown that Tanya wants to be a famous singer, but her talents go unappreciated. After moving to Green River, Cat R. Waul finds her singing the song "Dreams to Dream" in the streets, and is instantly entranced by her voice before even seeing her. He then takes Tanya under his wing, entitling her as "The Diva" and having her perform at a saloon for his gang, with Miss Kitty to be her mentor. She instantly wins over the cats with her song "The Girl You Left Behind". After the praise she has received by her "public", Tanya becomes somewhat delusional from her fame. Seeing Waul try to put the mice of Green River into a giant mouse trap during the film's climax snaps her out of it though, and by the end of the film she realizes she can still be beautiful by being herself, washing her makeup off.