Here me out. A human!rocky au except it's all technically canon compliant there's no magic and Rocky wasn't a human from the start instead there was a miscommunication...a pretty big horrifying miscommunication about the way in which Eridians are ambush predators.
Grace and Rocky probably had this conversation while they were in the middle of some taumoeba experiment and so something got lost in translation when Rocky tells him how Eridians hunt. "Eridians change. Need word for 🎶. To look like other. Hide." And Grace absent-mindedly types in the new word and says, "Oh camouflage. Like you hide in the landscape because you look like rocks? Or like a chameleon? Why haven't I seen you do it before?" And before Grace can launch into an explanation of what he means by "chameleon" Rocky cuts him off and uses a tone that indicates he thinks it's a stupid question and says there was no need to hunt therefore no need to camouflage also "Eridian culture rule. No watch" and then changes the subject and they quickly become wrapped up in a terrifying conversation about humans being persistence predators. "What the fuck. Statement." And the thing is if Grace asked a couple more follow up questions like he wanted to he would have found out that much like eating, "camouflage" is private because it's straight up body horror, puts them in a vulnerable state, and takes a huge amount of energy and Rocky changed the subject because he didn't want to freak him out because it's not "camouflage" it's mimicry/ shape-shifting. The other life forms on Erid aren't too dissimilar from Eridians and the process is still intense and exhausting so Rocky assumed that it would be impossible to "camouflage" as a human but at some point on their long journey to Erid, Rocky gets curious and while Grace is sleeping he tries it...except it's easiest to "camouflage" as something you're very familiar with and the human he's most familiar with...is Grace. And again Rocky assumes it won't even work but then he feels his carapace shifting and cracking and expanding and it's too late to back out because this is a process that once started cannot be stopped. Cue horrifying transformation that takes hours. Dr. Captain Ryland Grace then wakes up to his own personal space horror movie of finding a creature that looks exactly like him passed out on the floor just outside Rocky's airlock. Eventually things get explained and Grace tells Rocky that he needs him to change back or change into someone else because "I can't have a doppelganger. I will lose my ever loving mind." So after a very long hug, Rocky becomes Rocky again but they spend a lot of time looking through Stratt's library of everything to find a human for Rocky to study for future shape-shifting experiments and Rocky lands on the image of the newscaster from the beginning of the movie (James Ortiz) because he likes his hair. And I'm gonna wrap this up because I've written too much already but basically Adrian gets to keep their Rocky shaped mate, and Grace gets to have a human shaped Rocky maybe even a human shaped Adrian, and everyone lives happily ever after give or take some occasional body horror here and there














