For this prompt: Dean's dick starts talking to him and the worst part is that Sam can hear it, too.
(I added in Cas, Cas' dick, and Dean's ass, because DESTIEL FOR THE WIN!)
"Please tell me I'm drunk," Dean groans.
"If you were drunk, I'd probably be stuck inside some stranger while you got some strange," chides...
Well. Dean's dick.
Sam's nose scrunches up and he shakes his head, shuddering. "Shut it up! I don't want to hear this!"
"You think I want you to be hearing this?" Dean shouts. "It's creepy!"
"We need Cas' help," Sam says, hands clapped over his ears. I can't hear this, it's not happening, lalalalalalala...
'Dick' perks up, cheers, "Yay! Cas is coming!"
Lalalalala, this isn't happening, nope, nope, nope, nope, my dick did not just say that...
"Cas!" 'Dick' shouts. "Get down here!"
Cas appears, obviously distressed, and says, "Dean? Are you alright? Something's wrong—"
"Oh, hi, Dick!"
"What?" Dean's jaw drops, eyes wide.
"Oh, my, God, hi! Hiiiiii!" Dick trills, waving in Cas' general direction.
"It's happening to you, too?" Dean groans, piling every pillow he can reach into his lap and all the sheets. "Fucking hell.."
"Don't be so rude!" Cas' crotch chides. "A gentleman doesn't swear."
"Oh, my, God, dude, your dick's a Victorian banker," Dean laughs, hysterical—this can't be happening, this isn't happening, genitals are not anthropomorphised and capable of communication, nope nope nope.
Cas' dick huffs. "Rude. I don't know why you put up with these people, Castiel."
Cas covers his face in his hands, scrubbing at it. "Please, please, be quiet."
Dean keeps laughing, falling back on the bed. "I just—I'm going to die. I am going to shoot myself in the face and die, because this is horrible. I'm going to actually kill myself."
"Noooo!" Dick whines. "I wanna shake Cas' hand!"
Dean keeps muttering to himself, hiding his face in his bed. "Please, let me die, now, please kill me."
Sam just keeps humming, "Lalalalalalalalalalalalalalalalala...!"
Cas' face, flushed bright red, stays hidden in his hands. "This is very, very bad."
"No, Castiel—this is wonderful! Now I can become properly acquainted with Dean's more... tender side, shall we say?"
Dean groans. "Cas, please hand me my gun? I need to go blow my brains out."
"Do you think I'm enjoying this? My genitals were conversing with the whole of my garrison about the many wonders of your rear. It's mortifying." Cas flops down on the bed beside Dean and pats his back.
"Ooh! Hello."
"No," Dean says. "No!"
"A little lower, my pretty little angel," the seat of Dean's pants seems to say. "Hi! I've been waiting for you for quite some time, loverboy!"
"Oh, my, God," Dean groans.
"Hello, my dear," Cas' dick purrs, leaning towards the source of the sound. "You're quite the little minx, aren't you?"
"Cas? Can you please kill me?"
"No, Dean. We just need them to shut up."
"Rude," Cas' dick says, somewhat dazed. "Goodness, you are a delight, aren't you?"
Dean's ass giggles, blushing. "Silver-tongued behemoth, you."
"Hmm. Not a single part of that sentence that's inaccurate."
"...oh! Oh, my." More giggles.
"That's right, baby," Cas' dick growls, seductive.
Dean's dick says something, muffled, and his ass drags him onto his side so 'Dick' can speak. "I'm very, very interested in being a part of the conversation."
"Oh, I'd bet you are," Cas' cock says, cheeky.
"I'm vetting you, first, you know," Dean's dick responds, as stern as he can be. "Before you get anywhere near him, I need to make sure you'll treat him right."
"You bet your gorgeous self, I will." Cas' cock wobbles towards Dean's ass, as if giving him a once over. "I wouldn't mistreat him."
"And what about the Grabby Twins, hmm?"
"Why are they talking!?" Dean groans, rolling the blankets up around his waist and sitting upright. "Cas?"
Cas takes off his trench coat and Dean swallows, hard, as his dick says something muffled. Cas folds it up and covers his crotch with it. "I don't know what to do."
Dean takes a moment, clearing his mind of the image of Cas taking off his top layer—and then the suit jacket, loosening that tie, mmm, toeing off those shoes, then the socks, then undoing his belt, yummy-yummy, big thick cock, tying Dean to the bed with that tie, taking off the shirt, oh yes, tastycakes, delicious, SHUT UP BRAIN!
"Me, neither."
Sam takes his hands away from his ears. "Have they stopped yet?"
"No. We're sort of... muffling them," Dean says, grimacing.
"Eww."
"Yeah. We got nothing; can you do some research?"
"Yes. I'm going to the library, and I'm going to research there, because I don't want to hear your bits and pieces having a tea party." Sam grabs his bag, runs out the door, thanking God that he managed to escape.
"Is he gone yet? That tea party sounds like fun," Dean's ass coos, flirtatious, dripping with innuendo.
"I don't understand," Cas' cock says, and you can just hear it tilting it's head like a fucking confused spaniel. "How is a tea party fun for two sets of genitals and one completely magnificent rear?"
As Dean's dick and ass go about explaining the double entendre, Dean grows redder and redder, while Cas' trousers go all tent-y—mmm, that's a big tent, no, shut up.
"Oh. Oh, my. That sounds... very enjoyable."
Sam comes back in three hours, post-research glow making him look like a standardised floppy puppy, all adorable and satisfied from chasing a stick all afternoon. "So, there's no actual information, but there is a musical about talking genitals, which is weird, but it was actually pretty funny—what happened here?" He points towards the bed, toward's them, half-curious, half-terrified.
"Oh, we just had to give 'em what they wanted so they'd shut up," Dean says, tugging on his boots. He stands, shifting his weight, wincing a little.
"I had no qualms with it," Cas retorts, grinning with just his eyes. Dean tugs on a flannel shirt, unfortunately, not before Sam spots about seventeen hickeys.
"Well, yeah," Dean brags, stretching. He steps into Cas' space, smooths down his collar and lapels, straightens his tie. "There you go."
"Oh, eww!" Sam groans, turning and leaving the room.
Cas settles his hands on Dean's hips and kisses him softly. "My genitals were right about your rear—magnificent."