Obviously, I was mocking myself with Mittens.  If you're going to make your main characters all dress as animals, well... you gotta make fun  of it.  Mittens is my favorite character to draw because I always laugh while doing it.  His mouse... crown... thing is an allusion to a riddle I read in a book I forgot the name of, and have been trying to get ahold of for a while.  
"What's the safest place for a mouse's nest?"  
"...Behind a cat's ear."  
The mouse heads  are styled after kitsunae, a fictious mouse from one of my other stories, who used to ride behind my ear, although I could never remember which one.  As a random note, shortly after drawing this I saw a Kids in the Hall episode where they dressed as cats, and one of them had their hair styled just like this.  O.O  Well, I suppose there aren't that many ways to do it realistically.