Write something that has a hat in it. A made-up story, or the real, true adventures of some intrepid hat that you have known.
You could write about the social function of hats by asking yourself what certain hats communicate and represent. How can a hat promote group identity? How do hats cause misunderstandings?
Hats have many functions, one of which is fashion.
Write whatever you like, as long as there is at least one hat in it.
When you have finished, give your work a title and write the date on it, too.