The same handful of voice actors
Well, okay, good for them. But why are producers afraid to diversify?
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"Time flies like an arrow. Fruit flies like a banana."
You don't need a huge cast. The small cast works great. All you ever need is Dan, Chris, and Elise and who ever or what ever is the antagonist of the week. To many VAs would ruin it.
shareThey would have to pay them. If the main people can do more than one voice they really don't need to add more people.
Many shows on cartoon network do this. Animes do this too.