Amanda is a young girl who serves as the creator and anchor for the imaginary friend Rudger in the attic of her family home. She is implied to have created Rudger approximately three years, three weeks, and three days before the story's events, a period that coincides with the emotional loss of her father. Following her father's death, she lives with her mother, Lizzie, who is often preoccupied with running their shop, leaving Amanda to navigate her loneliness through the power of her own imagination.

Amanda’s personality is defined by a vibrant and unrestrained imagination that allows her to transform mundane spaces into fantastical adventures involving flying, fighting monsters, and traveling to impossible places. Despite her youth, she exhibits a strong sense of loyalty and determination, particularly regarding her promise to Rudger that they will always protect each other, never disappear, and never cry. While she can initially appear self-centered or oblivious to Rudger’s fears, her deep care for him becomes her primary driving force when he is threatened. She tries to remain strong and brave in a difficult family situation, though her fierce protectiveness stems from a fear of losing another loved one as she lost her father.

Amanda’s central role in the story is as the creator of Rudger, whose existence is entirely dependent on her memory and belief in him. The plot is set in motion when the sinister Mr. Bunting, a man who consumes Imaginaries, arrives at her doorstep. In a desperate attempt to save Rudger from being devoured, Amanda dashes into the street and is struck by a car, leaving her hospitalized and unconscious. This accident severs the connection to her Imaginary, causing Rudger to begin fading away. Her role transitions from active adventurer to the unconscious anchor that Rudger must fight to return to, making her recovery and the restoration of her memories the central goal of the narrative.

Key relationships define her character arc. Her bond with her mother, Lizzie, is one of love but also distance, as Lizzie struggles to balance work with parenting and has forgotten her own childhood imaginary friend. This dynamic highlights Amanda’s fear of growing up and losing the magic of her inner world. Her relationship with Rudger is the emotional core of the story; he was born from her tears and grief, and he represents the part of her father that she is not ready to let go. Her school friends, such as Julia, represent a contrast, as Julia is pressured by her own mother to abandon imaginary play, underscoring the societal pressure to mature.

Amanda undergoes significant development as she confronts the hard truth that she cannot keep Rudger forever. While she initially makes a promise that they will never be separated, the events of the story force her to mature. Upon waking and being reunited with Rudger, she comes to understand that as she grows older, her imaginary friend will inevitably fade from her daily life. This acceptance does not signify a loss of imagination but rather a mature understanding of memory and grief. She learns that even if Rudger disappears, the memories and the love they shared will always remain a part of her, allowing her to finally process the loss of her father.

Notable abilities possessed by Amanda include an exceptionally powerful and vivid imagination. Her creative energy is so strong that she can give life to a highly complex and sentient Imaginary like Rudger, who possesses his own thoughts, feelings, and fears. Her imagination allows her to construct elaborate, multi-sensory fantasy worlds filled with distinct characters and rules. Furthermore, her emotional conviction is so powerful that even when she is unconscious, her subconscious connection to Rudger keeps him from completely disappearing, demonstrating the strength of her will and her refusal to let go of what she loves.