Why did the voice actors change?

Janine was changed because RGB's massive success, despite not following the formulas of the time, made ABC jittery. They hired a bunch of "experts" who told them that Janine was too abraisive, rude, unlikeable, ect. and demanded that she be toned down into the same sort of bland Mommy Figure prevalent on Saturday Morning cartoons at the time: More detail in an interview with J. Michael Stracyznski on Proton Charging]: http://www.protoncharging.com/ghostbusters/articles/feature_rgb_jms.html The changes to Janine only applied to the ABC episodes, so in all other licensing (ie the action figures, the Now comic book) her original appearance and attitude remained intact. When the changes failed, the producers asked Stracynski to return to the program; he was too busy to do so, but did contribute a few more scripts, most notably "Janine, You've Changed", which explained the changes in-continuity as the work of a "Makeoverus Lotsabucks" posing as her "Fairy Godmother" Venkman's voice was changed, according to movie and Real Ghostbusters producer Michael C. Gross, because Bill Murray complained that the cartoon voice (Lorenzo Music) didn't sound enough like him (even though Real Ghostbuster Peter Venkman didn't look like him at all) This information came interview posted on [[Ghostbusters HQ: http://web.archive.org/web/20041216191647/http://www.ghostbustershq.com/interviews/interviewmichael.php