She is voiced by Elizabeth Debicki.
She is a small, brown rabbit, has brown eyes and wears a yellow shirt. She is also 1 ft tall.
Mopsy is a smart, feisty, and stubborn rabbit who is a rebel.
Having recently lost their father the rabbits are looking for revenge against Mr. McGregor and surprisingly succeeded after he dies of a heart attack out of nowhere.
This celebration is cut short however when McGregor's nephew Thomas moves into his uncle's land and manipulates Bea into becoming his girlfriend. Due to this, the animals decide to rage revenge against Thomas.
Mopsy and her friends use their tricks to kick the couple out of the house.
During the end credits, it is shown that Bea, Thomas, and the rabbits eventually moved to London together where Thomas has his own toy shop and Bea begins to write and illustrate books based on Peter and his friends.
- Like in the novels Mopsy is Peter's sister and the eldest of three triplets with her two younger siblings being Flopsy and Cottontail.