Whistlin’ Dixie
Tom Clancy’s character - Jack Ryan
Ivan Emmetovich, Ph.D.
Ignatius J. Reilly
Emperor Ig.
Jesus Christ. 
deleted.
SonnyBoy
what?
Dr John Dorian (Scrubs)
Carpenter on Wood
Kyle Broflofski
Prince Kamehehe Biatch
and the obvious follow-up
Eric Cartman
Sport
Deputy Sheriff Barney Fife
(Kelso’s nickname for him in early episodes; he later admitted he called all newbies that because he didn’t want to ever have to remember their names)
NoBullets
Frodo Baggins
Precious Mule (as in “drug mule”- get it?)
I’ll rejoin the threads with
Eric Cartman
Big Boned
Sideshow Bob
DieBartDie (I expect he gets banned quickly)
Peter Parker
Annulled
Satan
CouldItBe…?
Dr Benjamin Franklin Pierce (and please do not say “Hawkeye”)
[del]GuessMyName[/del]
Too late.
TheEgoThatWalksLikeAMan
King Arthur
Cuckold Swordstone
Vincent Vega
GottaTakeACrap
Simon Cowell
I don’t think Simon Cowell is fictional, dude.
Sniper (cuz he, y’know… Gimme a break, I’ve never watched the show)
Thomas Covenant
Shucks, how did I miss that? Um…Eleanor Vance (Haunting of Hill House).
Unbelievable!
Dave Lister