Katie Kaboom: Good, personally thought the shorts were very one note so I won't miss them at all.
Buttons and Mindy: Those ones I could take or leave (And the best of lot was the one where they paired up Mindy with The Brain.) Though kind of funny not to see them back to parody all of those inspiring dog movies that popped up in theaters in the past few years. Is what it is.
Rita and Runt: Booo! I guess even with Broadway still down they couldn't get Bernadette Peters back for some new material.
Hopefully the new characters will be worthy replacements/improvements and they're ditching the Hip Hippos (The least funniest segments in the series in my opinion) as well.
Guessing it has more to do with Runt pretty much being a Rain Man parody, and that's definitely more frowned upon in 2020
I kinda feel that’s a bit unfair to the Rita character, a spontaneous Broadway cat singing at inappropriate times is funny enough on its own.
It could be that writing team just doesn't feel there's enough interesting scenarios to make the pairing work as a recurring element in comparison to the Warners or Pinky & the Brain. I think they will show up at some point, but more likely as a novelty once or twice a season.