Boom. Let's do this. Explanations to follow, maybe. Some of these may be repeated.
Anderson: Lucas Black
MissZooey: Cynthia Nixon
Doc Happening: Peter Gallagher, if Peter Gallagher were a late night deejay for an oldies station.
Merriweather: Stephen Fry, in Hitchhiker's mode
BobClark: Now that I think about it, I'm going to have to go with the just-above the fray but still quick with a quip Adam Scott
Bobby Bear: Ben Daniels
Tati: B-movie actor extraordinaire Joaqium De Alameida, the "Spanish Phil Hartman"
Humanoid: Bill Pullman, because your posting about "Faith in Film" makes me think of that show he did about the end of the world
Nordling: Jesse Plemons
KidInTheHelmet: Bill Simmons, sportswriter
Dickson: William H. Macy
Feral: Jeff Anderson
Arjun: Willam Dafoe, simply because you have the best avatar ever
Dre: Sam Rockwell. The easy answer's Zach Galifinakis, though.
Mr. Cellophane: Patrick Wilson
Hocken: David Tennant doing an american accent
joeypants: Nicolas Cage
Spike: Who's the lead on the Inbetweeners, the guy with the great deadpan? That kid.
Jake: Ben Foster
LisaNY: Debi Mazar. Many people think she's shrill. I think she's awesome.
Schwartz: Wendell Pierce
Mattolli: Bill Paxton
Ryan S: I'm going to go left field and pick Ian McShane here, because I get a kick out of hearing Ian McShane narrate informative posts about sound
Diva: Wanda Sykes
Cameron: Ed Westwick. You know why.
DJ Dylan: Heart! Also, Patrick Fugit
Greg Clark: Rob Lowe (or Cougar Town's Dan Byrd)
tommy five tone: Guy Pearce or Paul Bettany
Princess Kate: Kristin Schall or Miranda July
I know I missed a lot of people, but that's off the top of my head and I need to think about some of these more. Round two will come soon, but I have to get up in five hours.