Calvin is an ordinary boy from a comic strip. However, he has a powerful "tiger" ally named Hobbes, and a great imagination. He has spiky blond hair and usually wears a red shirt with black stripes. He is somewhat fire-based.
He has two additional forms. First, he dons his Stupendous Man cloak and hood, and becomes Stupendous Man. However, unlike the comic, he gains the ability to burst in flames. The second is a custom creature called Nebular. Rather than getting energy from fire, in this form he gains it from the cosmos. He has two planetoids circling him like a molecules. He also has a metallic sheen to his flesh in this form.