Leonard Peacock is a fictional character from the novel "Forgive Me, Leonard Peacock" written by Matthew Quick. The story follows Leonard, a high school senior who plans to end his life on his birthday while reflecting on his troubled life and relationships. Throughout the day, Leonard interacts with several key figures, including his former best friend and a mysterious girl, which helps to reveal his struggles with loneliness and the desire for connection. The novel explores themes of mental health, friendship, and the impact of choices on one's life.