Jack, I'm scared.
—Jack's sister, to Jack Frost
Jack Frost claims his memory during his time in the snowy mountain's crevice, then and there remembering his sister. The scene first moves onto his mother bidding him and his sister a safe trip. It then cuts to Jack ushering his sister to stay still, who was standing on the thin and cracked ice of the lake.
He persuades her to think of the situation as a game of hopscotch and to slowly move inch by inch. Jack saves her and instead accidentally maneuvers himself onto the same cracked surface. The ice gives away below him, and he falls to his death, drowning. It was because of this act of love that The Man in the Moon made Jack into an immortal and chose him to be a Guardian.
Jack's sister has straight brown hair, reaching between her elbows and shoulders. Her eyes are of a similar brown and she has a noticeable beauty mark under her right eye. She is seen in the flashback to wear a brown and red dress with white and brown diamond designs decorating the bottom. She was also seen to wear ice-skating shoes.
She was also a true and spitting image of Jack Frost back when was a human (considering that they were siblings).
She appears during the early colonial scene talking to a man when Jack arrives to the village as Jack Frost.
After the battle of Jack and Pitch in Antarctica, she once again calls for Jack, causing him to remember he still has his memories. After Baby Tooth taught Jack how to use the Tooth Box, she makes an appearance in Jack Frost's flashback of his human past. The flashbacks showed Jack some of the fun memories he did have with her and also showed him the moment when he save her from the ice. These memories made Jack realize that he always has been a Guardian and gave him the courage to fix his mistake and save the Guardians and the children of Earth from Pitch.
She was mentioned once after by Jack's cheery proclaim of once having a sister and being her "Guardian."
Her last appearance was when Jamie told Jack he was scared, causing Jack to remember a similar situation between him and his sister on the ice and thanks to the memory he realize what his center was.
- "Stop tricking us."
- "Jack, get down from there!"
- "Jack, I'm scared."
- "No, we're not!"
- "Yes! You always play tricks!"
- Interesting to note, Jack's little sister somewhat resembles Jamie Bennett. It is possible Jamie is either a descendant from Jack's little sister, or maybe even her reincarnation, which might be the reason Jack felt drawn to Jamie.
- Baby Tooth has a similar beauty mark on the bottom of her right eye just as Jack's little sister does.
- Sophie Bennett and Jack's sister have similar hairstyles, bangs pushed over their right eye.
- Pippa and Jack Frost's sister are voiced by the same voice actor. (Due to this, many fans began to claim this name for Jack's sister.)
- She can be spotted talking to an adult during the early colonial village scene. (When Jack returns to the village as Jack Frost.)
- Unlike her brother, she wears shoes through her whole appearance.
- Although her age is never mentioned, she's supposed to resemble Jamie Bennett, meaning she is supposed to be around the age of 8-10 years old.