I'm going to guess it's not the voice that's creeping you out, it's the facial expressions. He does that because as a voice actor he has to exaggerate his mouth movements to make the words understandable 100% of the time, and after all these years (he's been doing voiceovers for a long time - probably even before Magellan on Eureka's Castle) it's probably impossible to just quit that habit cold turkey.
To be honest, he also doesn't look like he really wants to be doing the Good Night Show... as a writer on the show in the days of Melanie and likely the most seasoned actor remaining on the set, he was probably the best choice they had and they made him do it. The look in his eyes just says "I don't want to be here, I'd rather be behind the camera, thankyouverymuch."
I still wish they'd get rid of Star... now *that* character gets on my nerves... gimme a scalpel, I'll take it's tonsils out.