Stupendous Man is one of Calvin's many alter egos and an attempted superhero by Calvin. Calvin puts on a red mask and cape wich his mom made him, and pretends that other people (mostly the women in his life that he hates) are villains or monsters. When things begin to tilt away from his favor, he takes off the costume, and becomes "mild-mannered millionaire playboy Calvin" (a reference to Bruce Wayne, the secret identity of Batman) once more.
Stupendous Man is Calvin's second most-frequently employed alter ego, even though, according to Calvin, Stupendous Man has only won "moral victories" and not physical ones. He usually gets in trouble.  Stupendous Man is also Calvin's most powerful alter ego, achieving such feats as flying a telescope lens into the atmosphere and turning time back a day. However, these powers are largely wasted, either on supervillains Stupendous Man cannot defeat or on ultimately futile plans, such as getting mild-mannered Calvin another day out of school. During one comic, Calvin made a chant for Stupendous Man, however, it appears he cannot spell "Stupendous":
- S for Stupendous!
- T for Tiger, ferocity of!
- U for Underwear, red!
- P for Power, incredible!
- E for Execellent physique!
- N for ...um... something ...hmm, well I'll come back to that...
- D for Determination!
- U for ...for... wait, how do you spell this? Is it "I"?
Calvin never finished his chant. Miss Wormwood stopped him. We may never know what Stupendous man stands for.
On October 30, 1987, Stupendous Man made his debut appearance, albeit in a dramatically different costume than his famous crimson look. This costume was minimalistic at best, apparently including only a simple domino mask and cape. Stupendous Man's first costume only appeared in three panels of the same strip, then vanished forever. Watterson of course, elaborated on it. It was the strip where Calvin was mulling over going down on the slide. Through Calvin's own eyes, it was off a high-rise skyscraper Metropolitan building.
While Stupendous Man's second costume drew from an eclectic range of pre-existing superheroes, this first costume was clearly based off of the costume of the DC Comics superhero and Batman sidekick Robin. In addition to both the domino mask and cape, Stupendous Man's first appearance borrowed much from the status quo of the Batman line of comics, notably the internal monologue (although Stupendous Man's was in the third person, as opposed to the comic book contemporaries first-person tense) and the glaring down on the city streets from above a conveniently placed skyscraper.
The only power Stupendous Man demonstrated in this costume was "ultra-sonic hearing," and this was matched by an apparent fear of heights.
The next appearance of Stupendous Man began with Calvin announcing that Calvin's mother had made him a superhero costume, suggesting that this strip may be apocryphal to the Stupendous Man canon. In the epilogue to the final story, Calvin's mom threatens to take the Stupendous Man costume away for good.
Stupendous Man's G.E debut in recognizable form occurred on November 2, 1988, when Calvin's Mom made him a superhero costume consisting of a cape and cowl. Although the first two comic strips in this costume clearly show this as the entirety of the costume, it was the third strip (and Stupendous Man's first Sunday appearance) that fully defined the familiar costume of Stupendous Man: yellow boots and gloves and a gold belt, augmented by the crimson cape and cowl and a red spandex jumpsuit.
Unlike his first incarnation, this Stupendous Man was clearly self-motivated, seeking only to fulfill Calvin's best interests, which usually meant circumventing Calvin's homework. This leads Calvin into conflict with all major females in his life, doing battle with Crab Teacher, Annoying Girl, Mom-Lady, and Baby Sitter Girl at various points. Invariably, Stupendous Man is defeated, although he did achieve a pyrrhic victory against Susie.In Stupendous Man's final appearance, however, Calvin bemoans the loss of heroes in today's society, then dons the Stupendous Man costume (implying that it wasn't taken for good), declaring that, "as usual, the hero business is up to me."
- Crimson Bolt
- Mysterious Masked Man
- Champion of Liberty
- Defender of Free Will
- Defender of Freedom
- Advocate of Liberty
- Friend of Freedom
- Opponent of Oppression
- Lover of Liberty
- The Amazing Marvel
- Foe of Tyranny
- The Masked Man of Mega-Might
- The Whirlwind Wonder
- Champion of Liberty and Justice
- Ultra-sonic hearing
- Stomach of steel
- Augmented speed and strength
- High-speed vision
- Stupendous powers of reasoning
- Stupendous powers of concentration
- Stupendous muscles of magnitude
- There is another strip that ran Calvin as a superhero, but it is unknown if this is Stupendous Man.