@Senshi:
It's not too late, though. The third season could go back to the random episode pattern. I vote Royce for Miss Monday, Mr. 5, and Gedatsu.
Really? I always thought Sean could pla- of course he'd play them.
As to how I think those characters would work out:
Wanze: Dan - I always imagined him with the voice of the Noodle dude from Parappa the Rapper (LC Lapen really brought that back up). It's a similar voice.
Eneru: Royce - Two words: ghetto and white
Mr. 5: Royce - Black guy who talks fast and mumbles
Mr. 9: ??? - Austin Powers FTW
Ms. Monday: Royce - Maybe an impression of his sister.
Gedatsu: Uncle Sage - Nuff said.