Claire appears as a young child with fair skin, greyish-green eyes, and blonde curly hair that is kept in twin tails by pink ribbons on the sides of her head.
Claire usually wears a long, pink and frilly dress with pink ribbons attached to her dress as well.
On the back of her head is an extra mouth with razor sharp teeth and a faint grin, and this mouth takes place around her nape.
Claire in the movie has a shy and insecure personality, this is shown how she very rarely talks and speaks at a soft spoken tone.
Her insecurity steams from her backmouth, and she feels embarrassed to eat with it in front of new wards, as shown in her interaction with Jacob.
When Jacob enters the destroyed home where the peculiar children used to stay at, Claire, along with the other children is seen spying on Jacob while he was wondering around the house.
Claire is later shown playing with The Twins in the backyard of Miss Peregrine's home.
During supper time, the other children begin to eat supper, but Claire does not. When questioned why she isn't eating by Miss Peregrine, Hugh interjects saying that she is embarrassed to eat in front of Jacob. When insisted not to be embarrassed, she proceeds to eat her chicken leg with her backmouth, which suprises Jacob.
After supper, Claire and the other children watch Horace project his dreams, only to have his projection prematurely ended due to its nightmarish content. Afterwards, Claire and the other children go outside and watch Miss Peregrine reset the loop.
Claire is then shown being comforted by Miss Avocet, due to her fear of having to leave her loop. Later after Mr. Barron breaks into the loop with Jacob held hostage, Miss Peregrine orders Claire and the other children to enter the other room while she is being captured, this is to prevent them from all attacking Mr. Barron.
After Mr. Barron leaves with Miss Peregrine in captivity, Claire and the other children prepare for the Hollowgast that is sure to come. When the Hollowgast breaks into the house, Claire is evacuated by Jacob along with the other children.
After this incident, the children decided to use the sunken ship by the shore in the loop, that Emma used as a hide out in the past to get to the loop in Black pool ( this was where Mr. Barron and the other wights set up their machine to redo the experiment they did using ymbryne's essence to gain immortality, and this same experiment is what caused them to become Wights and Hollowgasts)
When they get to Black Pool, Claire and The Twins begin to fight of a fellow Wight of Mr.Barron, named Miss.Edwards, along with Bronwyn, Fiona and Olive, who were fighting of another Wight. In the next scene, Claire and the twins continue to dodge Miss Edwards' knife attacks, until Miss Edwards decides to try to grab Claire from behind, only for Claire chomp on Miss.Edwards arm using her backmouth, In excruciating pain, Miss. Edwards is then turned to stone by the twins.
When the fight with the wights and Hollows were over and the ymbrynes were free, the children leave the loop in Black pool and decide to go back into the loop Miss.Peregrine created. ( After the point where the Nazi's dropped a bomb on the children's home, the loop was not reset, so then time continued to move foward to September 4rth 1943, rather than being reset by Miss.Peregrine )
Backmouth: Claire's peculiarity is backmouth, as it states, Claire possesses a large mouth at the back of her head (specifically, around her nape) which has multiple razor sharp teeth that can eat a large chicken leg clean within seconds, and can nearly chomp off a wight's with one bite and cause excruciating pain.
Claire's peculiarity is inspired from a monster in Japanese urban legends, called the Futakuchi Onna, which has a backmouth. However, unlike Claire, the Futakuchi Onna can use her long hair to grab her targets and feed it to her backmouth.
It is unknown if Claire can eat with her actual mouth that she also uses to speak with.
Raffiella Chapman (the actress who played Claire) is almost identical to her book counterpart.