There were 236 different words in Dr. Seuss’s 1957 book The Cat in the Hat. So Bennet Cerf, Geisel’s publisher and co-founder of Random House, challenged Geisel to write a children’s book with only 50 different words, and they bet $50 on the outcome. In 1960, Dr Seuss delivered Green Eggs and Ham with exactly 50 different words. He won the bet and the book has sold ~10 million copies over its lifetime.