My subtitle is _____ because _____.
My friends page is called _____ because _____.
My username is ____ because _____.
My default userpic is _____ because_____.
My journal is called Dragon V's Ramblings because I identify strongly with dragons (largely the eastern variety), my first name starts with V and I tend to ramble... which is probably (and at times painfully) obvious to anyone who reads through a few of my posts :-p. Rambling helps me process things and over the years I've found that I really love writing (I certainly enjoy it more than I used to when I was in school).
My subtitle is Compulsive, Neurotic, Anti-Social, Paranoid but basically Happy because it's a surprisingly fitting (albeit slightly exaggerated) quote. I forget where I found it, but the original quote was a bit long so I edited it down to a usable length and all these years later it still amuses me so I've kept it around.
My friends page is called Friends, Fiends, and other Disreputable Characters because it started out as a typo (dropping the r in friends) when I first started customizing my LJ many years ago and it amused me so it's stuck around through a few different iterations. The disreputable characters bit obliquely (and in good humor, I assure you) alludes to a Groucho Marx quote, I would not join any club that would have someone like me for a member. It's another one of those little things that just cheers me up when I see it.
My username is dragonvpm because it was available when I created this LJ 8+ years ago (wow, I totally forgot my lj-versary a couple of months ago). It's fairly easy to remember but unique enough that I can usually get it on various online sites. I also have that as my personal domain and I use it for instant messaging. At this point, it's my most persistent online persona.
My default userpic is me in a welding mask because it amuses me. I only just changed it a couple of months ago, before that it was my da Vinci dragon icon. I dislike having my picture taken, but a while back someone I was close to was lamenting how I never took pictures of myself and since I was doing some welding at the time, I decided to be cooperative-ish. To this day it still makes me chuckle and it's a convenient picture to use online when I want to maintain some anonymity or when I'm grumpy/bitter about life etc...