Spoilers, season 4.
Hunger was how Jimmy got to know Castiel at first.
He didn't know what to expect when the angel took him. It wasn't as if there was a guidebook anyway, slipped between the pages of the illustrated New Testament for Sunday school classes. At the time, all Jimmy had wanted was for the angel to fix the chaos that his life had been plunged into. He'd been chosen, he'd been chosen, but all that meant was that his own faith was driving a wedge between him and that which he loved most.
Which should have been God. And - which Jimmy is starting to realize - might not be any more, because he misses his family, he loves his family, and every time he struggles back to self-awareness, all he thinks about is his family. Not God.
He hadn't been prepared for the angel.
The reverse seems to be true as well. Castiel knows the basics of dealing with four limbs, even if social norms are entirely beyond him, like not staring at people too long in bus stations, or knowing their intimate secrets at a glance. Castiel knows the basics of possessing an outer form. What he isn't good at is everything inside that body, starting with the primal guts all the way up to the heart and mind.
Castiel doesn't grasp the concept of food. Castiel doesn't understand hunger; he deals with the sensation by ignoring it, enforcing a sheer unfamiliarity between himself and starvation that does not allow for fraternization.
Because hunger is nothing Castiel had to worry about, he doesn't.
But Jimmy can't. He isn't good enough; he isn't that lucky. As his spirit trails along with Castiel, trapped in a vague half-awareness with only flashes of clarity, he can feel the warning blare of starvation firing off in his belly and mouth. He can feel the pain. It's like being in a fever, forever, illness pinning you to your bed like a butterfly. He can sense his stomach endlessly churning out acid and healing itself, he can experience his muscles cannibalizing themselves for energy before the presence of the angel makes them intact. He isn't sleepy all the time, at least - he isn't thirsty, which was a no-pun-intended miracle, but his body keeps wanting to consume. Its automatic processes continue relentlessly even when there isn't anything to digest.
His body keeps telling him it wants to eat. It keeps telling him, loudly, that he is on the brink of starvation.
You won't die from this, Castiel informed him blandly when the angel first noticed the frantic pitch of Jimmy's concern. Nothing else.
Castiel does not eat. Castiel doesn't sleep. He doesn't need to. Toxins, by the same process, are converted automatically; Castiel doesn't sweat except when he's really distracted. He doesn't smell, he doesn't sneeze. The grace bestowed upon him by heaven keeps him in perfect condition, healing his vessel continuously. It's part of the same unconscious reflex that keeps a human body breathing and blinking, so that anytime an angel drops into a meat sack, the body doesn't asphyxiate itself ten seconds later because the angel forgot.
Which answered another question Jimmy didn't really want to know: angels don't defecate.
Angels don't need to do a lot, unless they want to. Living counts among the things that do not interest them. Their bodies are rides; they're puppets, flesh coats, three-piece-suits made of person. Bodies are necessary conveniences, because otherwise, living beings can't be counted on not to go deaf, blind, and insane from being around an angelic presence. Human is what they wear. Not what they are.
And this was how Jimmy first started to understand angels, really understand them, as not just stereotypical fluffy cherubs or mechanical soldiers. They have the privilege of choosing. They have the luxury.
But when your body is perfect, your vessel guaranteed intact and working at all times, there isn't much else to do. Jimmy never thought before about how much of life was spent living, but it turned out to be a lot. Dressing, stretching, yawning, trying to stay awake. Trying to fall asleep. Making food. Eating it. Washing up afterwards. Staying clean. Being alive. Being afraid.
Without any of those things to concern him, Castiel spends his time in other ways. The angel likes to people-watch a lot. He reads trashy bodice-rippers back-to-back, always the same series - some author named Charlie or Chuck who likes to specialize in overblown prose. Jimmy endured exactly one dose of bad writing before deciding it was enough; now he tries avidly to block out the world whenever he sees the angel reaching for a paperback.
Whenever Castiel isn't being spooky or illiterate, he spends his time communing with his brethren on a level which - thankfully - blocks Jimmy out completely, sending him wading through the fuzzy, endless helplessness that's been the entirety of his existence since the angel came. It leaves Jimmy half-asleep, but constantly aware, catching only brief glimpses of the outside world. Castiel rarely speaks to him, barely acknowledges Jimmy's presence at all, except to offer up the shortest of reassurances.
Even when Castiel is sitting still - which is most of the time, angels don't need to fidget - his determination is perpetually in motion, like a star told to momentarily root itself to earth. Purposeful. His willpower burns without ever going out. It's fueled by faith or determination; Jimmy doesn't know which. He suspects, for an angel, they're interchangeable.
Everything else can be ignored: hunger, sleep, pain, blood.
But ignoring things doesn't erase them. Jimmy bleeds; Castiel stops the bleeding, undoes the wounds, but first the angel has to notice them. Jimmy's bones are broken, and put back together as soon as Castiel decides they're important enough to repair. Pain is one of the things that can make its way through the black haze, as if Jimmy is a filter, a filter to feel what's going on and let the angel know, because it's easier than the angel using something without a soul. The host is a tool. Jimmy's a shortcut, all so that Castiel does not bother having to learn on his own, this is hunger. This is sadness.
This is want.
After one battle with a demon that leaves Jimmy struggling to stay awake, drowning in the pain - one long, feverish convulsion, crying out for anyone to hear him - Castiel speaks.
"Sleep, Jimmy." In line behind them, two teenagers start whispering loudly; one woman averts her eyes in embarrassment. Castiel doesn't lower his voice. "You're in the Lord's hands. You're serving the Lord's work."
After that, it's all downhill.
It didn't take very long for Jimmy to start to realize that his life is over - that, if his face ends up on a milk carton somewhere or an FBI poster or a suspect list for being a child molester due to wandering around playgrounds with a constant trenchcoat, Castiel doesn't care. God does not care. Castiel can't be bothered to observe human conventions; he obeys a higher power, a greater law. Jimmy hadn't really thought about either phrase literally before, but after seeing them in action, he knows just how fanatical they could be.
He used to believe in the existence of that authority. Lord, make me an instrument of Your will, he'd pray. I only exist to serve You. Make me into a vessel for Your grace. Allow me to help carry out Your desires, oh Lord. I live only to act as Your instrument.
He prays a different way now.
Once he started missing his family, Jimmy couldn't stop. He couldn't stop remembering his wife, all the good times, the way her body fit into his when they were curled up on the couch together. The way she'd eat ice cream. All the things he loved about her, the way she'd put her hands on her back and stick out her stomach like a little girl, rounded in the summer light, her hair coming down in sticky tangles on the back of her neck. Spiritual love didn't compare. God didn't hug you - God sent down angels that got you stabbed and set on fire.
Demons fight Castiel, but it's Jimmy who gets hurt; Castiel only experiences nerves being damaged, muscles being torn. The angel has no instinctive fear of being crippled, knows no reflexive urge to flee from a monster in the dark, is prey to none of the thousand primal instincts that have kept the human species alive through all the cold nights on the earth. Castiel can touch fire and not flinch back.
Bereft of those limitations, the angel is able to do anything he wills. Castiel's fearlessness is terrifying - both for the demons, who love being housed in flesh, and for Jimmy, who wants his own back.
If he ever gets out alive, Jimmy's already resolved that he will never be insensitive to the feelings of his trenchcoat again.
He rolls back to himself somewhere between one city and the next, between one inexplicable assignment and the next. They all blur together now, just one endless order: serve, serve, serve. He can feel Castiel like a cool sheath over his thoughts - cold, but not soothing. As a boy, he'd touched an electrical generator outside his school once, felt it humming with a currant that seemed to penetrate directly into his blood. The angel is the same force. Instead of his wife, instead of his little girl, Jimmy has an angel. Instead of people who love him, he has an angel -
"That's enough for now, Jimmy." Castiel is speaking aloud; Jimmy has long given up on trying to explain to the angel that looking crazy isn't in Jimmy's best interests. "Don't be afraid."
Do you understand love? Jimmy protests into his mind, into the only space left to him while his body sits on the bench in a bus station and waits for some other rendezvous that will end up with Jimmy in multiple fractures. And not this 'God is love' doctrine, I know that.
"God is what's right, Jimmy." The angel's voice does not waver. "You're limited in your understanding. I know this must be hard for you. I'm sorry for that. I know you don't really mean to resent Him. This is simply your confusion talking."
Okay, then, human love. Love makes us feel connected. To something bigger, something else, someone else - like my family. My family, Castiel -
"God's children love and protect one another."
Lucky for us humans.
"We love and protect you as well."
Do you? Even in the echo of his own thoughts, Jimmy doesn't sound convinced. Is that what this is?
"You wanted this."
I wanted to help my family. My wife was going to leave me. My daughter - who knows what my daughter was thinking. I would have lost them because I was chosen.
"You would have lost them if you weren't. Now you can help them." Castiel sounds perfect, perfectly confident, perfectly assured - as if that certainty is enough to justify anything Jimmy has to endure. No amount of pain can overturn that judgement. No protest will suffice.
Then Castiel is up, on the move, on alert, shaking Jimmy away like a horse with a biting fly. The bus station dims and slides sideways.
Before being submerged again in the feverish haze that his life's become, Jimmy has time for one more thought - one last heresy before becoming regulated to a mere tool once more. Castiel can't be lying. Castiel can't be lying. Jimmy's family will somehow be protected because of all this. The alternative would be too much.
He doesn't want to think about a world where angels can deceive him. He doesn't.