I feel like a policy for making sure cast credits for animated series are all following the same system needs to be put in place.
I asked specifically when adding cast to this show:
https://www.tvmaze.com/shows/4107/spider-man/characters
What to do about main cast. It was agreed that since Spider-Man was the titular character, it didn't matter if Paul Soles did 8 different voices in an episode, he would only ever be credited as the main role he appeared in and guest starring as the rest. If a show is specifically citing that character is a star, then sure they should be added as such, which is what I've done on other animated series:
https://www.tvmaze.com/shows/1957/superman-the-animated-series
The supporting characters here would appear as Stars in certain episodes and were credited as such but some would mostly be credited in guest starring capacity.
So why do we have so many supporting characters as stars of The Simpsons? Surely the main family would be the only stars, I know voice actors are just credited in the show titles and character names aren't featured. If a starring actor appears as a different character in any of the Marvel animated shows (for example), I've added them as guests as the majority of the time they'd only appear once or in a few episodes.
If not we are ending up with characters been credited as stars like this:
https://www.tvmaze.com/characters/239165/the-simpsons-duffman
52 appearances in over 700 episodes
https://www.tvmaze.com/characters/836963/the-simpsons-old-jewish-man
32 appearances
An argument has been brought up that a character such as Milhouse may appear in more episodes then those characters above, but we have numerous guides on the site in which recurring characters appear across various seasons in every single episode of a show, yet they don't automatically get credited as a star because of it.



