Here he talks about the audition; in this entry he has a happy flashback; and he further describes his work on the episode here.
I like the guy, and I root for the guy. Wheaton does voice work now as well (I hope I get to see the animated short he did called Kyle + Rosemary, which sounds ultra-sweet), and it wasn't until I ran into an episode of Diagnosis Murder while channel-surfing (he guested as a National Park ranger) that it dawned on me how good a voice Wheaton has. He's also done a great job of self-examination, much of that on his blog and in his books; he realized that he was really an arrogant prick for a lot of his adolescence, and since then he's done his best to be a better person.
He had a brief-but-memorable role as a homeless murder suspect on CSI (I need to see that episode); now he's gotten to strech his acting muscles on primetime TV again. (Hmm. He keeps doing CBS roles. Maybe next he could do a scene with Pauley Perrette on NCIS...)