At the Guardian he named his top ten pseudonymous books. One title on the list:
The Cat in the Hat by Dr SeussRead about another entry on the list.
I once read a biography of Theodore Seuss Geisel and learnt one snippet of biographical information that I've never forgotten. Whenever a journalist asked where he got his ideas, Dr Seuss would reply that he found them on his annual visit to Über Gletch, a small town in the Austrian Alps, where he went each year to get his cuckoo clock repaired. Here's another nice fact about him: Dr Seuss didn't just invent his own name, he made up the name of an imaginary daughter too, and even dedicated one of his books to her.
The Cat in the Hat appears on Liz Pichon's top 10 list of funny books with pictures and Kate Kellaway's list of the 10 best illustrated children’s books.