One thing I've always found interesting about Rick Prime is how he addresses other people who aren't Rick.
Like in Solaricks, he calls apocalypse Jerry "little guy" and said he never got too close to the concept as if he has never actually seen a Jerry up close. He also tried to calm Jerry down, and his behavior, at first, was almost... Polite? I just think it's strange!
How he addresses Morty is also strange.
Most Ricks' we've seen never address Morty as a grandson, and most Mortys' never address their Rick as their grandpa. Summer does, but not Morty. Kind of odd, in my opinion.
But Rick Prime does address Morty as a grandson and as a teenager. Here's some lines he says that stick out to me.
"Did you talk to me or a little kid around here?"
"Hey, original grandson, this is super weird."
He cried "grandson" when he was knocked unconscious by Evil Morty.
"We can be like Batman and Robin."
"Oh, you don't want those schematics, buddy. Those are for grown-ups."
"He's fourteen. What's gonna happen the next time he gets mad at grandpa?"
Is it just me, or is Rick Prime the only Rick who actually views Mortys' as kids/grandkids? Lol! It's just funny to me. We just don't get to hear Morty call Rick his 'grandpa' enough, and we certainly never hear Rick call Morty his grandson. They almost treat each other more like best friends. While other Ricks' just view Mortys' as shields or tools.
I don't think Rick Prime has actually spent any time with anyone besides other versions of himself. Maybe that's why he doesn't know much about Jerrys' or Mortys' in general? He did have a sympathetic reaction to Uncle Slow though, so you never know! Our grandpa Prime is an enigma we just don't know much about, sadly.
I hope we get more backstory for him one day!