Muppet Babies, on CBS
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This ran from 1984-1991. There was a sort of fantasy flashback scene in Muppets Take Manhattan with some of the Muppets... maybe just Kermit and Piggy, I forget... as babies together. Which of course they never really were. But in this Saturday morning cartoon, many of the Muppets stayed together in a nursery, as babies, where they were cared for by Nanny. And they had lots of imaginary adventures and stuff. Also Robin came to visit sometimes when he was a tadpole in a fish bowl. That was weird. Okay, the whole show was weird. Muppets are weird. That's what's so great about them. Right? Wish I could think what else to say.
In 2018, a CGI reboot began airing on Disney Junior. I happened to see a couple episodes of it once when my cousin's kids were watching it, but it's not something I care about at all.