I suspect it is to underline the cartoonish, melodrama of the news in the TDKR world. Andrea commented about that very subject in the featurette. Hard to say about the voice cast theories, because only the main cast members have been confirmed so far, but your suggestions are probably on the right track. Ariel Winter is voicing Carrie Kelly, I think she nails it. Not feeling Peter Weller's voice for some reason. Maybe I'll change my mind when I hear the final product on DVD.