Hello -

I usually lurk more than post, but I thought I'd throw my 2 cents in for what it's worth on a couple of the characters.  I have always pictured Butters as a little guy like Danny Strong -  the short, Jewish guy who played Jonathan Levinson, one of the mad trio of sorcerers during one of the Buffy the Vampire seasons.  As for Bob's voice?  I've always heard him in my mind as John Cleese of Monty Python fame.  He has the British Accent and the risque range to pull off the naughtiness when required  .  As for Susan - I've always kinda pictured her as a Roselyn Sanchez, who played agent Elena Delgado in Without a Trace.  She's Hispanic with the high cheekbones and she can play smart and savvy.

Just throwing that out there.