Cynthia Brisby is a supporting character in Don Bluth's 1982 film The Secret of NIMH and a minor character in the 1998 sequel The Secret of NIMH 2: Timmy to the Rescue. She is the youngest daughter of Mrs. Brisby and Jonathan Brisby and the younger sister of Martin Brisby, Teresa Brisby, and Timothy Brisby and is the most curious and innocent of the four.
She was voiced by Jodi Hicks in the first film and Whitney Claire Kaufman in the sequel.
Cynthia is a very sweet, playful, innocent and slightly tomboyish yet beautiful little girl and is the youngest child in the family. She likes it when Auntie Shrew comes over to visit. She is 4 years old (by human age).
The Secret of NIMH
Cynthia is first seen playing with her doll in the Brisby house where she, Teresa and Martin are home alone until Auntie Shrew arrives asking for Mrs. Brisby.
She tells Auntie Shrew that Timmy's sick and and fidgits with her scarf. She later witnesses the argument between Auntie Shrew and Martin. As this happens, When their mother returns, she scolds her children for the argument. As their mother gives Timmy his medicine, Cynthia tries to go see Timmy, but Teresa pulls on her bow to restrain her. She asks is Timmy's gonna die and her mother answers that he's just sick and the children carefully and quietly watch as their mother tells them the cause of Timothy's illness: Pneumonia.
Later, she is seen with her older siblings when they see Jeremy the Crow suspended by his own string and Cynthia innocently calls him a "turkey" and he was repeatedly asked where their mother was, but he was told by Mrs. Brisby not to tell them where she is. He eventually tells them that she and the rats will move their home to a better place from the farm.
She is then shown where the house sinks in the mud, calling to her mother for help. She tries to hang on but falls into the muck and grabs onto Teresa's foot. The kids nearly die, but were fortunately saved at the last minute when Mrs. Brisby uses the power of the stone to save them. She is last seen with her whole family at the end of the movie.
The Secret of NIMH 2: Timmy to the Rescue (1998)
Cynthia, now 8 years old, appears in the sequel for a short time in the scene before Timmy leaves for Thorn Valley. But, playing a smaller role than Martin and Timmy (along with Teresa), she only appears briefly.