In J. M. Barrie’s Peter Pan, Peter says he can never grow up.
Refusing adulthood is the character’s defining idea. Peter remains a child in Neverland, where he leads the Lost Boys, fights Captain Hook, and treats ordinary adult responsibilities as alien or undesirable. The phrase “the boy who wouldn’t grow up” became one of the story’s most enduring descriptions.
Peter’s refusal is not presented as a simple superpower. Barrie’s story links it to memory, loss, responsibility, and the painful fact that children eventually change. Wendy can visit Neverland, but she belongs to the world of growing up; Peter’s identity depends on remaining outside that process.
This answer is different from Peter’s ability to fly. Flying is something he can do with the help of happy thoughts and fairy dust in many adaptations. Growing up is the condition he rejects, making it the central answer to this literary question.