We know the cat in the hat, the grinch who stole Christmas, and those surprisingly yummy green eggs and ham. But who was Dr. Seuss? His real name was Theodor Seuss Geisel, and in addition to creating some of the 20th century's most popular children's books, he helped spawn a media empire that has pumped out everything from clothing to audiobooks. After spending a good chunk of the 1930s in advertising, as well as penning humor pieces for the likes of Vanity Fair and Life, Geisel published his first children's book in 1937. After a stint in the Army that saw him writing propaganda films in World War II, he relocated to California and unleashed a string of instant classics, including Scrambled Eggs Super! and How the Grinch Stole Christmas! But his greatest success came in the '60s. Simplifying his writing style for beginning readers, he produced The Cat in the Hat, an international smash. Leery of marketing techniques, Geisel personally approved most adaptations of his work, be it movies, music or toys -- a wise move, as it ensured most spin-offs would retain that Seussian quality. Cancer claimed Geisel's life in 1991. He was 87.