I actually wasn't on board with this ship at first—it felt like a joke pairing taken too seriously. But the dynamics really do push the narrative somewhere interesting. Gnarpy's chaotic, self-absorbed energy forces Spud, who's usually just the deadpan observer, into a role he's not built for: the exasperated caretaker. You see this arc where Spud starts out just tolerating the nonsense, then slowly begins to anticipate it, and finally, against his better judgment, actively enables it. The best fics use that shift to explore a kind of reluctant codependency. It's less about romance and more about two broken systems figuring out how to run as one glitchy unit. That's where the character growth sneaks in, buried under all the absurdist humor.
A lot of writers get stuck just replaying their canon dynamic, but the ones that dig deeper use the 'shaping' to ask what each character lacks. Gnarpy needs an anchor; Spud needs someone to pull him out of his own head. Their arcs become about filling those voids, often in really messed-up, unhealthy, but strangely heartwarming ways. I read one where Spud starts adopting Gnarpy's reckless jargon, and Gnarpy begins double-checking plans, and that tiny exchange of traits felt like a more genuine arc than any epic confession scene.