Cottontail is Peter's sister and a major character of Peter Rabbit.
She is voiced by Daisy Ridley who also plays the role of Rey from Star Wars: The Force Awakens.
She is a light brown rabbit, has brown eyes and wears a green vest. In the 2012 series, she wears a pale yellow shirt with a plaid yellow dress with orange trim and yellow butterflies on her pockets and turquoise underlings. She also wears yellow bows on her ears.
In the 2018 film, she's paranoid, feisty and headstrong. In the 2012 TV series, She goes on adventures with Peter. Even though she's only 2 years-old, Cotton-Tail is a very sweet, loving, kind, beautiful and caring rabbit. She looks up to her big brother, Peter, and her big twin sisters, Flopsy & Mopsy. She even wants to be just like him and go on adventures too. Instead, she can stay in the rabbit burrow with Flopsy & Mopsy. She can be trouble when she wanders off into the woods because of predators. At times she is proven to be very sneaky. Cotton-Tail gets scared of the dark and her big twin sisters, Flopsy & Mopsy take care of her.
Role in 2018
Cottontail, her siblings and Benjamin spend most of their days picking on Mr. McGregor and stealing his vegetables from his garden. They are friends with a local woman named Bea who spends her time painting pictures of the rabbits as well as the surrounding nature.
Peter invites all of the woodland critters and then takes over McGregor's old house. When Thomas kicks out Peter and his friends and begins to secretly wall up to the garden, despite Bea's objections.
Peter and his 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.
In the 2012 TV series, Cottontail and Shrew have a one-sided friendship. Cottontail loves shrew and thinks he's cute, while Shrew thinks Cotton-Tail is annoying. Cottontail dresses Shrew up as her dolly, but Cotton-Tail has friends and Shrew just left Peter's burrow.