"So: either it was an hallucination that masked the flavor and texture of the bugs you were eating, or some god has gone out of Her way to show you favor!" He twitches the hat aside and brings his palm down on the top of Rincewind's head with a colossal SMACK that's louder than it hurts. "How dare you curse the gods when they've directly stood between you and death? Show some gratitude!!!"
"Oh, Scraggly-san," he says (not unkindly, because Rincewind is more fun than he's had since autumn), "you just walk right into these things, don't you." He lets the silence draw out, long and horrible and full of fangy grins. Finally, in a much more cheerful voice, "All right, then--" Hand still on Rincewind's head, he shoves down until Rincewind is on his knees, and delicately balances the plate and hat on top of his head for him again. "--Show me."
I know, and Xel is openminded on the topic. But even if it did happen that way, someone had to either create the sandwich out of ether, or an unconnected team of people had to harvest and treat the wheat, raise the chickens, collect the eggs, pick the berries, process the sugar, develop the yeast, bake and slice the bread, assemble the sandwich, and magic it under the rock. So he still thinks Rincewind should be grateful. u.u
(Not that he isn't mostly grandstanding here almost entirely because it's fun and he never gets to do this sort of thing...)