Theodore Seuss Geisel was removed as editor of the campus humor magazine while a student at Dartmouth College after too much reveling with fellow students. In spite of this prohibition-era setback to his writing career, he continued to contribute to the magazine pseudonymously, signing his work “Seuss.” This is the first known use of his pseudonym, which became famous in children’s literature when it evolved into “Dr. Seuss.” His introduction to animation and illustration came during World War II, when he worked on military training films and developed a character named Private Snafu. The Cat in the Hat is considered the defining book of his career. More than 200 million Dr. Seuss books have been sold around the world.