Jackson Jekyll is the great grandson of Dr. Henry Jekyll. He is part human and part fire elemental, as his father is a fit element. Due to his mother's Jekyll/Hyde lineage, he has a monstrous alter ego named of Holt Hyde. Jackson longed to be a monster until he discovered his alter-ego whom he now wars with. Believing himself to be fully human most of his life, he has grown up among monsters in a world where the two groups mutually dislike each other, probably causing him to be cautious and shy but not easily intimidated just because someone's a monster. As well as careful and kind, Jackson is a dedicated scientist and one of the best students at Monster High. Jackson's alter ego is Holt Hyde. His transformation is triggered by loud music. Jackson is a friendly guy who enjoys playing casketball, though he has a geeky fashion sense and is sometimes picked on by other students. He appears to be the only human student at Monster High, making him confused by his apparent normalcy in a school full of monsters. He once asked Draculaura to bite him, as he was afraid they couldn't really be friends when school started. Draculaura was able to talk him out of it, but she could tell he was still depressed. Draculaura noted in her diary that he was unfazed when he met her father, who normally creeps out both humans and monsters. He seems much more wary around monsters, most likely due to being bullied at school for being a "normie." He even went as far as to say that he "didn't belong," and that no one would want him at Cleo's party. While the Monster High students are aware of Jackson's/Holt's dual nature, older monsters can sense his duality. This is evident in Draculaura's "Basic" diary when she overhears a conversation between her father and Jackson, where Jackson makes a light joke about stakes. Her father later cryptically tells her that Jackson is more than he appears. Because of his shy personality, his body language is nervous, and he tends to hunch his shoulders. Jackson has dark brown/black hair with blond tipped bangs, blue eyes and a pierced left eyebrow. He has a yin and yang symbol between his shoulders however if it was, then Holt would probably likely have the tattoo as well. He wears black framed glasses with a button up yellow shirt which he had half untucked and a green, black and grey checkerboard sweater vest with black trim. He wears a blue bow-tie, blue and green high-top sneakers, grey pants, and a black belt with a silver buckle. He is roughly 5ft 11in.