From season 1 of The Real Ghostbusters:
Pre-Halloween jobs are getting harder for the Ghostbusters. Could there be some major supernatural threat behind this? J. Michael Straczynski, before he earned sci-fi credentials with Babylon 5, cut his teeth writing for cartoons like The Real Ghostbusters and the original He-Man & The Masters of the Universe. "When Halloween Was Forever" allows him to demonstrate a flair for comedy, as well.
I think I can see why Lorenzo Music was replaced as Peter after 1 season. It wasn't because he left to do Garfield & Friends, but the fact that he has one basic voice, which gets tweaked a tad depending on the character. And Ray (Frank Welker) sounds more like a grown-up Fred Jones, doesn't he?