I keep thinking about the fact that Eridians seem so much stronger and sturdier than humans, so what humans-are-space-orcs thing could Grace even do that would freak Rocky out... and then I remembered humans are persistence predators.
So picture some years in the future when the xenonite suits are so safe that Grace's class can now take field trips into his biodome. Rocky's there because this is a big moment for everyone involved and also he just loves listening to Grace in his element. One of the more mischievous kids tries to sneak off from the group and there are plenty of chaperones but Grace is the first to notice.
His posture changes, goes focused but loose in a way Rocky's never seen before as he peels of from the crowd. Rocky just stands there, stunned, as he watches his sweet, gangly, goofy, clumsy blob of a friend turn into a hunter. Grace circles around the pebble, slightly crouched, head turned and honed in, arms loose to the sides, and maybe the little one notices and does that nervously excited giggle-squeal thing kids do when they're being chased and tries to get away, but Grace expertly corrals them. He doesn't even have to run for it, he just pens the kid in, lunges-
And takes the little pebble by the claw to lead them safely back to their peers. And just like that he's Grace again, smiling and joking and tripping over his improvised shoelaces. Rocky hasn't been scared of Grace since first contact. Have you seen the guy? ... but for a second there his instincts were telling him to run.
