From an interesting NYTimes article on a new exhibition about Dr. Seuss's love of hats:
As editor in chief of Beginner Books at Random House in the late 1960s, Michael Frith worked closely with Geisel, sometimes into the early hours of the morning. When they were stumped by a word choice, Mr. Frith said, Geisel would often bound to the closet and grab a hat for each of them — a sombrero, or perhaps a fez. There they would be, sitting on the floor, Mr. Frith remembered, “two grown men in stupid hats trying to come up with the right word for a book that had only 50 words in it at most.”
My favorite detail is that he apparently had a secret hat closet hidden behind a bookcase. Imagine trying to pull a copy of "Oh the Places You'll Go" from the shelf only to have the bookcase open up, revealing a secret closet--and instead of finding some deep dark secret, you find a room filled with hundreds upon hundreds of goofy hats?