Franken is an artificial creature originally created by Dr. Frankenstein. He serves as one of three primary attendants to Taro Kaibutsu, accompanying his prince from Monster Land to the Human Realm. Standing 297 centimeters tall and weighing 252 kilograms, Franken possesses an imposing stature, making him the group's largest and strongest member. Despite his formidable appearance, he displays a consistently gentle and innocent nature.

His verbal communication is limited, typically restricted to monosyllables or single words, yet his fellow monsters understand his intentions and engage in full conversations with him. Franken functions as the group's "Dumb Muscle," lacking intelligence but providing essential physical strength. His personality sharply contrasts his appearance; he is insecure, kind-hearted, and emotionally vulnerable.

Within the trio of attendants, Franken embodies the "nice" aspect, counterbalancing Dracula's pride and Wolfman's laid-back demeanor. His loyalty to Kaibutsu-kun is unwavering, though he often endures mistreatment during the prince's tantrums. Franken has a younger sister named Grenken.

His immense strength features prominently in conflicts, such as battles against the demon group Demonish. Wolfman handles cooking duties, while Franken possesses no indicated culinary skills. Unlike Wolfman, who transforms when exposed to round objects or full moons, Franken displays no reactive traits or shape-shifting abilities.

Across all media appearances, including the movie "Demon no Ken," Franken maintains his core characteristics: immense physical power coupled with childlike innocence and emotional sensitivity. His role remains consistent as the gentle giant who provides comic relief through his naivete while delivering essential protection. His established origin and relationships persist without significant evolution or background expansion.