Tinker Bell

Tinker Bell is a small pixie from Neverland. She is a companion of Peter Pan, but has a hot temper with a high jealousy towards Wendy. She becomes a Summon in Kingdom Hearts and also is one combined with Peter in Kingdom Hearts II. She is very small in size to the rest of the characters, and can allow them to fly using her pixie dust (also combined with the flyer's happy thoughts).

Kingdom Hearts
Tinker Bell is introduced to Sora, Donald and Goofy when they meet Peter Pan in the hold of Captain Hook's galleon. Tinker Bell informs Peter (she cannot talk) that she has located Wendy but has a deep jealousy for Wendy due to her growing relationship with Peter. Donald figures this out and gets hit by Tinker Bell. Tinker Bell later sprinkles the trio with her dust for later use of flight. Peter rescues Wendy and flies off somewhere, leaving Tinker Bell and the others to fight for themselves. Tinker Bell is captured by Hook and held hostage in a lantern - her life or the Keyblade is Hook's demand. Sora walks the plank instead and flies thanks to happy thoughts. Peter returns and saves Tinker Bell from Smee. After Captain Hook takes the plunge and is defeated, Tinker Bell reappears and tells Peter of something happening at the clock tower nearby. They go to the clock tower (Big Ben) in London where Sora seals the Keyhole. Tinker Bell seems to approve of Peter and Wendy's friendship at last and Peter asks Sora to take Tinker Bell with him as an ally. Tinker Bell is delighted to go with Sora. If one returns to Neverland, Tinker Bell tells Sora and Peter of the Phantom Heartless at the clock tower.

When Summoned, Tinker Bell's appearance is different from the other summons. For one, Donald and Goofy remain on the battlefield and Tinker Bell doesn't vanish after a certain amount of time. Instead she remains with Sora, continuously healing him and his allies until dismissed, and reviving him upon death (provided that Sora does not get hit the second his HP hits 0, Tinker Bell will fully recover Sora's HP)

Kingdom Hearts II
Tinker Bell returns with Peter Pan as a summonable, maintaining the same healing factor she did previously.