These are "peekaboo" ponies with jointed necks.
Ribbs - well, Ribbs is cute too. And he was for sale at the same time from the same seller and of course Whirly Twirl needed a friend to travel across country with him so he wouldn't be scared.
And yes, because I always headcanon little family/friend relationships for these ponies: Whirly Twirl and Ribbs are from neighboring pony families, and they are best friends who always play together. (And I think Paws, another Baby Brother Pony, will have to be the third friend in the group).
Again, yeah - my pony world is very gentle and very safe, and I think that's something I kind of need. (When I was a kid I also figured out elaborate family-and-friend relationships for my dolls and animal toys, and I don't remember there being any really "antagonistic" relationships, like "this character bullies this other character" and I suspect that might have been a reaction to what I experienced a lot in school....that I wanted an imaginary world that was kinder and safer than the real one.)