It all started on my cousin's Xbox and his copy of Halo 2. I was making my own account, and I wanted a random name and number, to follow Spartan naming tradition. So, Mike-042. (I later realized my cousin AND my uncle are named Michael) How does this matter?
Well, when I got Halo 2 Vista, I needed a gamertag. I originally wanted to be SchizophrenicSpartanII, but there weren't enough characters. So, I stuck with SchizophrenicMC (MC standing for Master Chief). I was incredibly into the games at the time. Well, back to the Mike part. I later decided to standardize the Mike-042 thing, and I had just finished playing this little journal-based roleplaying game with my friends, including Mike the Spartan, who had developed Schizophrenia and gone rogue. And I needed backstory for him. So, I fiddled around with last names, and came up with Mike Christiansen (Because I'm mostly Danish, by descent, and I needed a C name... Little did I realize, my cousin's name is Michael Coffaro.) (The long and short of it is, due to a genetic disease, as a child, Mike was placed into cryogenic storage and forgotten for about 500 years, and then was stumbled upon, thawed, and cured, and later recruited into SPARTAN-II)
So, SchizophrenicMasterChief became SchizophrenicMikeChristiansen. And, whenever I need a fake name, I use MC.
Oh, yeah, Schizophrenic. I just liked how it sounded at the time. Besides, you say "SchizophrenicMC" and it just rolls right off the tongue, you know?