Baby Tooth was one of the creations of Toothiana. When PItch Black's nightmares were kidnapping the other fairies, Baby Tooth was rescued by Jack Frost and later reunited with Tooth. Later, Baby Tooth accompanies Jack back to Burgess to return Sophie Bennett to her house. However, they hear a little girl's voice, which lures Jack into Pitch's lair. During this time, Baby Tooth and Jack were separated.
Pitch Black is revealed to be holding Baby Tooth hostage and threatens to kill her unless Jack gives Pitch his staff. However, Pitch goes back on his word, Baby Tooth manages to free herself, but is thrown into a ravine, Jack falling in after her. She later shows him how to open the tooth box. Jack later leaves her in Pitch's lair while he goes to find Jamie.
After the children's belief in the Guardians, Baby Tooth gains her ability to fly again. After Pitch is defeated, Tooth hugs Jack, causing Baby Tooth to humorously chastise her.
Baby Tooth was noticably brave, helpful, and friendly. She and formed a close friendship with Jack frost after he saved her from being eaten by a Nightmare.
Unlike the other fairies, who have blue feathers in the center of their foreheads, Baby Tooth has a gold feather, like Tooth. It's probably one of the reasons why Jack called her "Baby Tooth."
Baby Tooth has a beauty mark under her eye, just like jack Frost's sister.