"Dude," Dean muttered, his head lowered to the burger of which he had paused between bites, "you look massively awkward. It's making people stare. Slouch or something."
After a moment, Castiel shifted slightly on the bench opposite Dean, trying to make it look "natural," whatever that was. Dean insisted that looking "natural" was crucial, and that Castiel didn't, despite the fact that Castiel's vessel wasn't artificially constructed in any way.
The vinyl squeaked loudly beneath him, causing Castiel to freeze again. Dean laughed through a mouthful of ground beef and bacon. Castiel glared.
"God's sake, Cas, just eat something."
"I do not need to eat."
"You're in a restaurant. Everyone eats in a restaurant."
"I have no money for food." He had recently learned how to obtain goods by offering money for them, but although Castiel understood the concept, he had little idea of how many pieces of paper or metal a burger might be worth.
"Just have a fry or something."
"Sam is not allowed to take things from your plate."
Now Dean was glaring, his lips shiny with grease. "Cas. Seriously. How hard can it be? Hell, you might even like it."
Castiel looked at Dean's burger, skeptically eyeing the long aliphatic chains and carbon double-bonds of the trans fats dripping from the meat. There was a small puddle on Dean's plate, lipid bilayers gleaming golden on the surface of the water that had leaked from the juicy meat.
A suspicious glance at Dean's chest told him all he needed to know: a very thin layer of cholesterol had already begun to gather on the inner walls of Dean's coronary arteries, which Castiel had remade pristine. It wouldn't begin to pose a health problem for years, but Castiel wanted it gone already. He would have to tend to it the next time Dean fell asleep.
"No," he said.
"Your loss. What about a pickle? These are good pickles, Cas."
Dean shoved the plate toward him. It contained three bright green wedges of pickled cucumber, a heap of fries covered in ketchup and the scattering of onions, mushrooms and bacon crumbs that had fallen out of Dean's burger.
For no reason Castiel could name, the acetic acid in the pickle's juices vaguely disquieted him. He watched protons in the liquid jump back and forth between acid and water molecules.
"Aw, come on. What about a fry?"
"Dean, I have no need of sustenance."
"Yeah, but now I kind of just want to see you put something in your mouth."
Castiel squinted his eyes at Dean. Dean grinned unrepentantly.
"One fry, man, that's it. It's easy, you just open your mouth and shut your eyes; it goes right in."
Castiel vaguely suspected that Dean might be making a joke of him, but he couldn't tell. After a moment, he dropped his eyes to the plate again.
The potatoes had been fried in a combination of vegetable oils, but there was beef fat in them as well, distinctive triglycerides floating among the oleic acids. He squinted suspiciously at the chemicals providing golden colour to the vegetable matter until Dean poked the plate again, urging, "C'mon, Cas, just one."
Finally, Castiel carefully picked out a single fry that had not been touched by ketchup. The pseudoplastic viscosity of it did not appeal to him. A last glance at Dean showed that he was watching raptly, burger forgotten in hand.
Castiel placed the fry between his teeth and bit it neatly in half.
"...Okay, now chew."
"What, you gonna sit there with it in your mouth all night?" Dean was still watching him with an avid expression, and Castiel didn't quite know how to respond. "Well, how is it?" Dean prompted after another moment, looking anticipatory.
The potato turned to mush between his molars. Castiel felt sodium chloride dissolving in his saliva, its ions transferring tiny electrical charges into the nerves of his tongue. Countless little sparks sent electrochemical impulses racing along axons sheathed in myelin and up to Jimmy's spinal cord, through the brainstem and into his brain.
From beneath the layer of insulating Grace that Castiel had muffled Jimmy's overactive sensory system in, he felt a flicker of... something.
"Acceptable," he announced at length, placing the other half of the fry back down on Dean's plate.
Dean looked disappointed, and tried to hide it. "Whatever," he muttered gruffly, going back to his burger. "You don't know what you're missing."
Realizing belatedly that Dean had been looking for a more favourable response, Castiel felt crestfallen. It would have been so easy to please Dean if only he'd known how. He wanted to take his response back, but could not.
He pressed Jimmy's tongue against the roof of his mouth, searching for another flare of electrochemical response, something that he could follow with every fibre of his Grace for a hint of what Dean felt when he ate. But all he could sense was the polarity of his neurons' cell membranes reversing, returning to normal again.
No. He didn't know what he was missing at all.