It's not a luxury he has often, not with having to keep an eye on Sammy all the time. Even after Sam leaves, he doesn't get a chance really, not until Dad starts letting him handle his own cases and he has a few days alone on the road.
Then he'll go into the lingerie stores - thank god for malls and Victoria's Secrets - and buy things for his non-existent girlfriends.
He's never liked bras, too restrictive, the straps digging into his shoulders and bands not wide enough to fit around his chest unless they have giant cups, and that always looks weird.
No, he likes camisoles and panties, little boy shorts that ride up in back and show a little of his ass. They are always left behind, burned in the trash can because you can never be too careful.
In Phoenix, he gets his first negligee, a peach satiny slipdress that feels amazing on his skin. He comes all over the place that night, soaking it beyond cleaning in the sink, so he goes out and buys another one the next night. He stops for a little while after that, it's a little scary how much he likes the feel of the soft little dress with its lacy hem that falls on his thighs.
By the time he's itching to try something again, Sam's on the road with him and they're living in each others' pockets, just like when they were kids. He holds off for months, just on sheer willpower. He can't give Sam any ammo for their bitch fights.
He finally gives in after the lake spirit - he needs a different kind of release than the kind he can get with his flings and one-night stands. He gets himself a full-length negligee, navy blue silk with a beautiful full robe and then a room at a motel across town. He just sits for a few hours in front of the TV, letting the material slip and shift over his arms and legs. When he finally takes himself to the bed, he's so hard he can barely stand it, and he doesn't even need to put a hand on himself to come - he just slides the material against his cock until the sensation makes his eyes roll back in his head.
He can't bear the idea of buying an actual dress, so he steals one out of a witness's closet somewhere in Montana. She's a curvy girl, so he thinks the dress will be big enough, and it's a swingy little sundress, spaghetti straps and a full skirt. He stashes it so deep in the trunk there's no way Sam will find it before Dean can move it to the bottom of his duffel, wrapped in one of his flannel shirts.
It's just a cotton dress, not even a material that feels that good on his skin, but he can't stop looking down at the skirt, the way it sways gently and swirls around his legs. It's the first one he doesn't burn; the first one he takes care not to get come on. He stashes it back in his duffel and keeps it wrapped up in its flannel, safe from Sam's prying eyes.
The last thing he does before they leave to take Lilith out is to burn the dress behind the motel. There's some small part of him that dies there, hours before the hellhounds drag him out of the suburbs and down to the pit.
He should have guessed that Cas's penchant for horrible timing would manifest itself the first time he chanced a trip to the mall. It's more than a year after Cas breaks him out of hell; apparently dealing with Sam's addiction and his destiny and trying to prevent the apocalypse is enough to keep his appetite at bay.
It isn't until Sam decides to take his little vacation from hunting that Dean says fuck it. It's the apocalypse, and he's been thinking of it on and off since he talked to himself about it in 2014. Doesn't seem like there's any point in denying himself anymore.
He goes to the mall, but this time he spends time in the stores, talking to the salesladies, trying to get exactly what he wants in a size that fits. He's broadened in the shoulders, so it seems like strapless is his best option, but those dresses are so formal-looking he hesitates, especially when the women look at him like they can't believe his girlfriend would be a size 12.
One of the women suggests a corset, and he can feel himself get half-hard at the thought. He nods, silently, and they bring out several of them on tiny little hangers. He can't even take the time to process properly - he just picks the first one that looks sturdy enough to hold him. Once that decision's been made, he picks the dress he'd been hesitating to buy, a black full length dress, one that will skim his body like a second skin, and walks out of the store not five minutes later.
He's still trying to get the corset on himself - he hadn't realized what a bitch it was going to be - when he hears the rushing of wings. He's so thoroughly mortified at being caught in his silky underwear and half-strapped into the corset that he has no clue what to say. His usual sarcasm is miles away, awol along with his dignity.
"Is this a bad time?" Cas asks, and Dean's mouth drops open and twitches, trying to answer Cas or laugh or just catch a breath.
"Yeah, Cas," Dean says finally. "It's a bad time."
Cas looks him up and down, something that Dean's always found creepy when he was fully clothed; it's twice as creepy now. "Are you certain?" Cas asks. "A corset is easier to put on with two people."
Dean hangs his head. He doesn't even know how to explain to Cas everything that is wrong with that suggestion.
Before he can even try, Cas grabs him roughly by the shoulder and turns him around, unhooking the part of the corset Dean had managed to get closed and shifting it into position so it rests on his waist. He manages the hooks and eyes with a deft hand - maybe a bit of angel magic, it's so fast - and pulls the laces tight enough to squeeze Dean's ribs. It's a dizzying feeling, partially the loss of lung space, he's sure, but when he puts his hands on his waist and feels how small it is, he can't help laughing.
"That dress won't fit you properly," Cas says, and Dean can feel the blood rush to his face again. This is not how he expected things to go down if he got caught. Cas has him in the most vulnerable position possible and doesn't even have a clue. It makes him grateful for Cas's particular brand of ignorance where the social graces are concerned.
"Here," Cas says, picking the dress up and holding it for Dean to step into. "Let me fix that for you."
Cas slides the velvet up Dean's legs, over his compressed waist, and under his armpits. Dean can't do anything but hold his breath as Cas tugs the dress into place, shifting Dean's pecs in the corset and then into the cups of the dress - gentle touches that are more intimate than a lot of sex he's had. When he looks down and sees how perfectly he fills out the bodice, he marvels. He never would've never guessed he could have a bust like that.
When Cas zips him up, he can feel that material shift, like Cas's will is making it smooth over Dean's body the way the dress is supposed to fit. He's fully hard now, not entirely hidden by the dress, but when he walks over to the mirror and checks himself out, he likes the obvious sign of his approval.
Apparently Cas does too, because his simple, "You look quite beautiful like that," makes Dean blush in an entirely new way.