I think I started out with the RAF roundel - and that was because when I sign up for things these days, rather than spend ages narcissistically thinking up a really cool nickname (trying to combat one of my major flaws here), I just went with whatever song was on the stereo. And since I was listening to The Who, I thought a roundel would be appropriate.
Then I changed to a sorta demon dark lord thing, cos it matched my state of mind for a while. I was having to do a lot of manipulation and playing dirty, and found it quite liberating, sorta a little indulgence after years of repressing that side since I went clean. It was sorta fun to see the looks on the faces of people who had thought I was all Mr Nice Guy.
Then I changed to Q, just cos I really dig him - watching him is real fun for me cos it's like vicariously being able to enjoy acting like I wish I could get away with in real life. I went with the judge, cos I thought it was a good way to sorta remind people that besides the loopy, harmless and theatrical appearance of the ENTP, there's the "mad, bad and dangerous to know" side!