A Three Hat Day by Laura Geringer, illustrated by Arnold Lobel

From the back of the book:
R. R. Pottle the Third has a truly wonderful, extra-extraordinary collection of hats. But happiness eludes him. He is lonely and dreams of meeting a perfect wife - who will, of course, be wearing a perfect hat. One day, a day so bad that R. R. Pottle wears not one, not two, but three hats at once, his dream comes true in the best possible way.