Luffy always steals Zoro's food.
It annoys Zoro to no end, because he likes to eat, and he'd never admit it, but he likes the shitty cook's meals, too.
But Zoro's been noticing lately that it's only his plate that Luffy steals from. If he's not at the table for whatever reason, Luffy will steal right from the pot before he resorts to taking from anyone else's plate.
Zoro isn't one to over-think simple issues like that, but with Luffy… such uncharacteristic favouritism makes him wonder.
Makes him wonder a bit too long, actually.
So when Zoro looks down at his plate again, his hunk of chicken is gone, and Luffy is trying to give him an innocent grin even with his mouth full and meat sticking out between his teeth.
Zoro glowers as Luffy swallows the stolen food, and whacks his captain on the back of the head, calling him an idiot and taking another chicken leg to replace the pilfered one. Of course, it isn't long before he has to smack an elongated finger with a spoon to keep Luffy from snatching his potatoes.
But so long as Luffy only steals from his plate, he doesn't really mind.