The Blue Fairy is the tetartagonist of Disney's 1940 film Pinocchio. She is a magical being and Pinocchio's protector who, fulfilling Gepetto's wish, transforms Pinocchio into a living creature, and later into a real boy.
She also aids Pinocchio and Jiminy Cricket throughout the heroes adventure, both directly and from afar. One of only two female characters in the film (the other being Cleo), she is nevertheless one of the most powerful characters in the cast; it is the Blue Fairy who initially grants Pinocchio life, and who ultimately decides whether or not the puppet should become a real boy. The Blue Fairy was animated by Jack Campbell from live-action footage of Marge Champion, and was voiced by the late Evelyn Venable. She has since been currently voiced by Rosalyn Landor.
The wishing star is first referred to in the film's opening song (with the Blue Fairy herself perhaps referred to in the song as "Fate herself"). When Jiminy Cricket begins his story, the wishing star is looking over Pinocchio's village, and it and the other stars are 'shining like diamonds'. It is not mentioned again in the film until inside Geppetto's Workshop. After Figaro has opened the window, Geppetto notices the Wishing Star and wishes that the marionette Pinocchio becomes a real boy. Everyone in the workshop falls asleep; soon, however, Jiminy is woken by an ethereal glow caused by the star as it moves closer and closer to the window. Eventually, the Blue Fairy herself appears in the workshop, stating that Geppetto deserves his wish after the happiness he has brought to others. She walks to Pinocchio and, tapping the puppet with her wand, grants him life. She tells him that he must learn the difference between right and wrong in order to become a real boy. When Pinocchio appears not to understand, Jiminy interrupts to explain, and the Blue Fairy offers him the position of conscience to Pinocchio. Somewhat dumbstruck by her beauty, he agrees and is granted a new suit befitting his status. The Blue Fairy then leaves, reminding Pinocchio to "be a good boy, and always let your conscience be your guide."
The Blue Fairy next appears after Stromboli has locked Pinocchio in a cage; the showman intends to use the wooden boy to make an enormous amount of money. Ashamed of doing the wrong thing, Pinocchio attempts to hide when he sees the wishing star approaching the caravan, though both he and Jiminy are spotted. The Blue Fairy asks Pinocchio why he did not attend a school that day; lying, he concocts a ridiculous story that he was kidnapped by two monsters, who put him into a sack and threatened to chop him into firewood. As his lie grows, his nose becomes longer until it resembles a tree limb, complete with bird's nest. The Blue Fairy informs him that "a lie keeps growing and growing until it's as plain as the nose on your face". When Pinocchio promises to tell the truth from then on, the Blue Fairy returns his nose to normal and frees him from the cage with a tap of her wand.
She does not appear in person for the rest of the film - in keeping with her 'warning' as she frees Pinocchio from the cage that this is the last time she can help him - although she offers some indirect assistance. When Pinocchio is on Pleasure Island, while other boys were being turned into donkeys and then sold to salt mines by the Coachman, Jiminy warns Pinocchio to follow his lead to prevent the curse from taking a foothold, with his role as the Fairy's proxy allowing Pinocchio to escape his own transformation.
After the two return home and see Geppetto's abandoned workshop, the Blue Fairy, in the form of a dove, drop a message that Geppetto learned about Pleasure Island and set sail in order to rescue Pinocchio, but his boat was swallowed by Monstro the Whale. Presumably, this "bonus help" was due to the fact that Pinocchio had gotten back on track by listening to Jiminy (as well as ceasing his bad boy behavior unlike Lampwick) and that Jiminy would not have realized that Geppetto had been attacked by Monstro as they were making their way back to the village. Pinocchio's dangerous decision to try and rescue Geppetto (even over Jiminy's objections) was the final test in order to see whether or not he had what it takes to become a real boy.
Pinocchio's selflessness in rescuing Geppetto from Monstro costs him his life, as he drowns while saving Geppetto from the same doom. As Geppetto and Jiminy mourn Pinocchio's death, the Blue Fairy appears, saying that Pinocchio has proven his heroism and rewards him by returning him to life, reversing the Coachman's donkey curse, and ultimately changing him into a real human boy. She also gives Jiminy a golden badge, declaring him Pinocchio's official conscience.
The Blue Fairy has a kind and pure heart. Likewise, she fulfills Geppetto's wish merely because of his selfless and caring personality, following with her encouraging Pinocchio to choose the path of good if he wishes to become a real boy. In a later scene, she also scolds Pinocchio for lying, saying that one lie will lead to another and a good person should be honest.