Franken is one of the three primary attendants who accompany the prince of Monster Land, Kaibutsu-kun, on his journey to the human world. As a creation originally brought to life by the legendary Dr. Frankenstein, Franken stands as the largest and most physically imposing member of the group, with a notable height and weight that make his formidable presence immediately apparent. Despite this intimidating stature, which might naturally inspire fear, his personality is defined by a stark and endearing contrast. He possesses a consistently gentle and innocent nature, often described as a gentle giant with a kind heart.

Franken's verbal communication is extremely limited, typically restricted to monosyllables or guttural sounds such as "unga". However, this lack of conventional speech does not isolate him; his fellow monsters from Monster Land can fully understand his intentions and engage in complete conversations with him, creating a dynamic where he is intelligible to those closest to him even when he cannot form proper words. Within the trio of servants that includes Dracula and Wolfman, Franken serves a specific function. While Dracula is often portrayed as prideful and Wolfman as laid-back, Franken embodies the nice and innocent aspect of the group, acting as its emotional and moral heart. He is, in many ways, the archetypal dumb muscle, possessing immense physical strength but lacking significantly in intelligence, which often provides a source of comic relief through his naivete.

This lack of intelligence is counterbalanced by a deeply loyal and emotionally vulnerable personality. Despite his strength, Franken is described as insecure and kind-hearted, and he remains unwaveringly loyal to his prince, Kaibutsu-kun. This loyalty is often tested, as the spoiled and short-tempered prince frequently throws tantrums and mistreats his servants, with Franken enduring this mistreatment as part of his devoted service. His motivations are simple and centered on this loyalty, driving him to follow the prince to the human realm and to participate in the various conflicts that arise there, such as battles against the antagonistic demon group known as Demonish. His role is consistently that of the protector and the brute-force problem solver, using his incredible strength to defend his companions and overcome physical obstacles when more nuanced approaches fail.

Regarding his relationships, beyond his unwavering loyalty to Kaibutsu-kun, Franken has a familial connection of his own, as he has a younger sister named Grenken. This detail provides a small but significant glimpse into a background that extends beyond his function as a servant. Although his established origin remains fairly static across different media appearances, his interactions highlight the unique bond between the three monster attendants, who function as a surrogate family of sorts under the prince's command. In terms of notable abilities, Frankenstein's defining trait is his immense physical power, which is frequently called upon during conflicts. Unlike his companion Wolfman, who has distinct trigger-based transformations related to full moons or round objects, Franken displays no such shape-shifting abilities or reactive traits. He also lacks any indicated culinary skills, a role generally filled by Wolfman. His core identity remains focused on his physicality, providing essential protection and strength for the group as they navigate the challenges of the human world and beyond.