[K126] is a clan tag from "Team Fortress" and "Counter Strike". In real life it is the first character of a street were some friends and I used to meet to play RPGs. Second is the actual building number.
Mephisto is from the classic German book "Faust" written by Goethe. Mephisto is kind of a devil, however not really evil. He is the "wag" (my dictionary give these words for "Schalk": rogue, wag, fool). This stuck to me from my high school time.
Check this one out:
http://www.shrapnelgames.com/cgi-bin...3;t=002871;p=4