A quirky, sentient robot with a distinctive, makeshift appearance, created from various scraps and parts. Neptr is known for his cheerful and somewhat erratic personality, often displaying an innocent enthusiasm for life and a strong desire to be helpful. Despite his haphazard design, Neptr's earnestness and unique charm make him a memorable and endearing character. He often joins Finn and Jake on their adventures, bringing a mix of humor and heart to the storyline.