Geisel wrote The Cat in the Hat (1957) in response to a challenge that he write a book that first graders couldn't put down. He claimed the book took nine months because of the difficulties of using a limited number of words. Only one word("another") has three syllables.
Perhaps an a propos reminder for today: "Will you succeed? Yes, you will indeed. (98¾% guaranteed.)" Oh, the Places You'll Go (1990)
Green Eggs and Ham (1960) was the result of a bet between Geisel and Bennet Cerf, his publisher. Cerf challenged Geisel to write a book using only fifty words, which Geisel accomplished with this best-selling children's story.
"I meant what I said and I said what I meant, And an elephant's faithful, one hundred per cent!" Horton Hatches the Egg (1940)