He's actually Australian voice talent doing an American accent. Sometimes you can tell this when he's obviously unfamiliar with colloquialisms that apparently don't exist there. I specifically remember him once accusing Adam of making up words when he was not. I wish I could remember the episode, but it was a relatively recent one.

(Yes, obviously he doesn't write the script, but if he were familiar with it, you'd think that he'd have pointed that out to the producers and they would have changed it.)