"Wearing my hat"

Yesterday, it seemed like everyone was using the phrase, "wearing my ____  hat".
Where did that phrase come from? I really don't understand it. Actually, it reminds me of P.D. Eastman's book Go Dog Go. My favorite parts of that book are the exchanges between the yellow dog and the pink poodle, like this one: http://www.colliersinjapan.com/page32/files/first-hat-exchange.jpg (largely because my dad would read it to me in a hilarious way, expressing the pink dog's indignation perfectly.)

Anyways. What 'hats' do I wear? I prefer to think that I'm the same person, regardless of what activity I'm participating in, that the hat I'm wearing does not change the girl underneath. I don't know if that's true, but I hope it can be! The pink dog has some insecurity issues, going through all these hats to gain the attention of the yellow dog! (yes, I know I am over analyzing a children's book, but just look at her final hat! http://farm4.static.flickr.com/3231/2442393679_0898e1822e.jpg)

Also, point of interest - when I Googled for these pictures, I found that MOST people are under the misconception that Theodor Giesel (also known at Dr. Seuss or Theo LeSieg) wrote Go Dog Go. That is incorrect, it was written by P. D. Eastman, who also wrote Are You My Mother? another excellent book that was read to me as a child (for that book I remember my mother reading the line "you are not my mother. you are a SNORT." and the picture of the crane was absolutely terrifying because it looked like it had teeth! http://free.bridal-shower-themes.com/img/are-you-my-mother-snort_1.jpg)

So, in this conglomeration of metaphors and children's books, my question for you (because I always try to engage readers with a question) what 'hats' do you wear, and if you were to draw them, what might they look like? I always imagine the hat of a student looking something like the Sorting Hat from Harry Potter...the hat of a sister is a sunbonnet (like Laura and Mary Ingalls) and...what do you think? Maybe some of the pink dog's hats fit some of the roles you fill?