Works in the popular science genre commonly use humor to engage audiences, and it features heavily in What if? 2 as well as in Munroe’s other works. Humor can make even the driest subject matter engaging to a wide and otherwise disinterested audience. Munroe’s humor contributes significantly to the commercial success of his work and thereby to its effectiveness in communicating complex scientific concepts to a wide readership. The book contains many sources and forms of humor, from the absurdity of the questions themselves to the dry wit of Munroe’s prose, to the snappy punchlines and bizarre staging of the comic illustrations.

The very premise of the What if? blog and books is humorous. The application of real scientific principles—often viewed as serious, even intimidating—to absurd hypotheticals creates a comic juxtaposition. Many of the questions are from children, and the others convey a childlike sense of imagination and naivete. In everyday life, such questions rarely receive detailed answers or analysis by highly-qualified experts. Munroe’s doing so therefore highlights the fanciful nature of the inquiries and the joy he finds in them even as it validates them, making for a humorous dialogue between asker and answerer.