Runrun Felmère emerges as a recurring supporting character aligned with dark magic societies, offering intermittent aid to the central protagonists throughout their journey. She wields specialized snake-based magic, commanding serpentine summons and related mystical arts. Her role includes entrusting the wind spirit Gipple to the heroes, serving as their temporary guide or source of magical assistance.

A defining comedic element stems from her reluctance to reveal her name, acutely aware others find it laughable; this self-consciousness prompts her to avoid name-related interactions, especially after Nike erupts in uncontrollable laughter upon hearing it. During the events of "Doki Doki Densetsu Mahoujin Guru Guru," she develops romantic feelings for Sly, Nike's thief mentor, introducing a personal subplot to her appearances.

Her visual design sometimes features disguises or concealing garb, with one notable instance in the Cophal Kingdom arc revealing previously obscured physical attributes when she abandons a cover. Within the 2017 series, she displays meta-awareness by physically interacting with on-screen text elements like name bars.