Dean Winchester tries his best to hide his annoyance when he hears the knock on his door in the middle of the night. With a groan, he lifts himself off his bed and trudges towards the door. Sure enough, when he swings the door open, he finds himself facing the ex-angel.

With an exasperated sigh, he demands, "What now, Cas?"

But Dean immediately regrets his harsh tone once he registers Castiel's composure. There's mad panic in his eyes, his hands shake terribly, and his face is an ashen color.

"Cas, what's wrong?"

Castiel's lower lip trembles and he twists his hands around a rag, "I...I think I'm dying, Dean."

All drowsiness and exasperation evaporates from Dean and distressed concern takes its place. He grabs for one of Castiel's arms, gripping it tightly, looking at him sternly. "Why, what are you feeling Castiel? What's going on?"

"It's my abdomen, it's been agony for the past two days, but I didn't want to say anything. It feels as if a knife is carving out my insides, I think it might be Metatron regretting his mercy on me. Dean, what-"

The former angel's face scrunches into one of pain and double over, holding on tightly to his stomach. A thunderous growl fills Dean's bedroom, along with a pained groan from Castiel.

Dean's on the verge of panic. He can't lose him, he just can't.

He closes his eyes and tries to remember if anything suspicious had happened in the past two days he'd been with him. Realization sinks in and a smile begins to spread across his face.

"Cas?"

Another stomach growl and he's breaking into a sweat. "And this keeps happening. These noises have been relentless and they're accompanied with the sensation of my insides twisting and-"

"Have you used the restroom?"

Castiel lifts his head up to meet Dean's eye and tilts his head, "What?"

"The restroom. You know that little room by Sam's room. The one with the toilet in it. The one where we tend to disappear into after eating."

Dean barely manages to hold in the guffaw when Castiel's eyes become a squint. He has to bite on his lip when that squint becomes a vicious glare.

"I am dying and that's-"

"Cas, you're not dying. You just need to drop a load into the toilet."

"What load?" He asks suspiciously.

"The load of crap in your intestines. Just-just come with me."

Dean walks down the dark hall, into the tiny restroom, and flicks the light on. Castiel stumbles in, looking at Dean warily.

"That-" Dean points at the toilet, "-is where you drop a load. You put both seats up if you're going to pee and..."

Dean, with surprising patience, explains everything to him. About how the human anatomy works, more specifically about how the digestive system functions. Castiel is horrified at first, but is mostly relieved that his death isn't imminent. Dean further explains the mechanisms of the bathroom and how it will bring an end to Castiel's pains. By the end of it, half an hour has passed and Castiel's face is a bright red.

"Oh, thank you. For teaching me." He says at last, not daring to meet Dean's eyes.

Deans smirks, "Just come to me if you have any other questions about being a human being, man."

He walks out of the restroom shaking his head. Boy did he have a lot to teach this guy.