I think out of any of the caregivers he's had, Grace would be fussiest with Rocky, just because of how constant and open their contact is. Kinda like how kids can be super well mannered at a friend's house, but be "misbehaved" at home where they comfortable to express more negative feelings and opinions and stuff. It's not like he didn't think he could be himself with Carl or Eva, he just... didn't really go any further than pouting and glaring when he was small.
But Rocky is maybe a tiny bit of a bad influence. They like to argue for fun, and pick on each other affectionately all the time, and Grace finds himself expressing negative feelings more outwardly with him. He'll stomp his foot, and sag against the wall or over a table or even flop on the floor. He'll whine and complain and make a general fuss. If something serious is going on, it will of course be handled delicately, but little Grace is usually just cranky because he doesn't want to go to bed, or doesn't want to clean up, or he lost a game too many times. And Rocky seems to be immune to those this, which makes him even more frustrated in the moment, but means a heck of a lot to him. Rocky doesn't get mad, he doesn't get scared, and he doesn't get offended. He'll always make sure Grace is alright, and will affirm his feelings, but never backs down on things they've agreed on unless they're having a Big talk. He's safe and reliable and not going anywhere.
He saves the "grumpy tired stupid" for big Grace, but he's more than willing to say "Grace tired question? Grace need nap question?" in either a genuine way or a slightly provoking way depending on the circumstance if Grace is being a stinker for no good reason. Sometimes the answer is loud wordless whining, sometimes the answer is a denial and an apology, and sometimes... the answer is yes 😅
Rocky loves his pebble who is kind and silly but sometimes stubborn and fussy, Grace loves his (untitled but surpasses the need to be) who is thoughtful and fun but sometimes overbearing and sassy, and they're making something unbreakable together 💛
