This story was written as a birthday gift for the lovely sinnerforhire (even though I'm a few days late with getting this posted). To celebrate, everyone should totally go check out her stories, either here or over on AO3. She's written some amazing stuff for both J2 and SPN.

This story doesn't fit into any part of the canon timeline. I wrote it as being vaguely season 9-ish, but you can imagine it happening any time you want. Basically, this is just birthday fluff, and when it takes place doesn't particularly matter.

This was originally going to be a oneshot, but it ended up being longer than I intended, and I wanted to get at least part of it posted this week. Chapter 2 will be up as soon as I have a little more time to write.

"You know," Dean suddenly said, breaking the silence that had fallen over the car during the past half hour, "you'd think they could have at least shown us some gratitude for saving their asses."

From his spot in the passenger seat, Sam snorted. "Yeah, three grown men burst into a preteen girl's slumber party and start waving guns around. I think we should just be grateful that they didn't call the cops on us."

"Hey, those girls would have been werewolf chow if we hadn't got there," Dean argued. "We saved their whole party, they should give us something for our time."

Sam rolled his eyes. "You just want cake, don't you?"

"Damn right I want cake! I haven't had cake in forever, man!"

Sam shook his head and leaned his elbow on the armrest so that he could prop up his head with one hand. It had been about an hour since they'd crashed some girl's birthday party to finally take care of the werewolf that he, Dean, and Cas had spent the past week hunting. Now, they were heading back to the bunker, though considering it was already ten o'clock and they still had a fifteen-hour drive ahead of them, Sam figured that Dean would pull off pretty soon so that they could stop for the night.

Cas was stretched out in the backseat, and Sam had thought that he'd already fallen asleep – which wouldn't be surprising, really. Even though Cas had been human for a while now, he still hadn't fully adjusted, and tended to get worn out faster than the Winchesters did. Apparently he was still awake, though, because he said, "I've never quite understood the concept of birthdays."

Dean glanced over at Sam and raised his eyebrows, the way he always did when Cas showed how ignorant he was about human culture. The looks had increased about tenfold in the past couple months, as if he had more of a right to make fun of Cas now that they were officially dating (after spending years trying to insist that their awkward closeness and intense eye contact meant absolutely nothing).

"It's the anniversary of the day someone was born," Dean said, with more patience that Sam would have expected from him.

"Yes, I know that," Cas said simply. "But I don't understand the point of celebrating someone on the day they were born. They had nothing to do with the actual birth – if anything, I'd think that you'd want to celebrate their mother, as they were the one who actually had to go through the painful birthing process."

Dean glanced at Sam again. This time, Sam just shrugged and inclined his head toward Dean, trying to indicate that he was the one who had to handle this question. Cas was his boyfriend, not Sam's; Dean was the one who had to explain all the things that Cas didn't understand.

"I guess it's more celebrating the fact that they're alive, not anything they did," Dean said after a moment. "Like, 'Hey, you were born! Awesome! We're glad that that happened!'"

"I see," Cas said slowly. Sam turned around in his seat. Cas was still lying across the backseat, but now he was propping himself up with one arm, and nodding to himself. From the look on his face, though, he didn't quite understand what Dean meant, but he'd decided that he wasn't going to bother asking more.

"What?" Sam asked. "They didn't have birthday parties in Heaven?"

He'd meant it as a joke, but Cas – of course – answered seriously. "No, we did not. Time moves differently there, and anyway, none of the angels have birthdays. We were born during the first days of creation, but there isn't exactly a way to convert that into a date on the modern calendar." He was quiet for a moment, then added, "Perhaps that's why I don't understand the necessity. Angels have never needed a birthday, and we have been fine. Although, I've come to realize that humans require many things that angels do not, and the majority of those things are not bad."

Dean's eyes flickered toward the rearview mirror for a second, using it to look back at Cas. "I guess it's one of those things that you have to experience to understand."

"Yes, I believe so." Cas nodded, as though that settled the matter, and settled his head back onto his bunched-up trench coat. Though he no longer wore it everywhere he went, he had kept the coat, and now he was using it as a pillow. His eyes closed, and almost immediately, his breathing began to even out. Cas could fall asleep faster than anyone that Sam had ever met.

Sam could tell that the wheels were spinning in Dean's head. He had a sly grin on his face, like he was either incredibly excited or completely proud of himself, or maybe both. And it wasn't hard to figure out what this was about – he kept looking at the rearview mirror every couple of seconds, like he was waiting to make sure that Cas was fully asleep before he said anything.

Sam gave it two minutes – that should be long enough for Cas to find his way into lalaland – then turned to Dean. "You want to throw him a birthday party, don't you?"

For a second, Dean looked thoroughly put out at the realization that Sam had thought of this on his own, without Dean having to tell him about the plan. It only lasted an instant, though, and then he was grinning and nodding. "I mean, everyone should get a birthday, right?"

Sam nodded. He couldn't argue with that. And even though it had been a long time since the two of them had bothered to do anything special for their birthdays, he still remembered all the birthdays he'd had as a kid. Dad was almost never home, and when he was, the most he ever did was remember to throw a "Happy birthday" Sam's way when he wasn't too distracted by whatever hunt he was going to go on next. Dean, though, had always made a point of dragging Sam to the park to play (even after Sam started insisting that he was way too old for that), or using some of their food money to pay for pizza and arcade games.

Dean was right. Everyone should get a birthday party at least once.

"So, what day do we use?" Sam asked. "The day he fell?" That would mean that they'd have to wait until next year to celebrate, though. Sam didn't think that that was what Dean had in mind.

And sure enough, Dean shook his head. "Nah, something sooner than that," he said. "I mean, no time like the present, right?"

Sam thought for a moment. "You know, tomorrow's Thursday. If we're going to do this, then that would be the day." That just earned him a blank look, and Sam shook his head. "Cas is – was – the angel of Thursday, remember? I'm pretty sure he told you that at least once."

Dean just shrugged that off. "Angel of Thursday, huh?" he said, and sent another glance back at Cas. "Good enough for me." He took a second to glance back at the road – which as surprisingly responsible, for him – then turned to Sam with a grin. "In that case, let's get ready to party.

"Dude, how much stuff did you get?" Sam asked as Dean walked into their room the next morning with his second load of bags.

"Shut up," Dean grumbled, hefting them onto the table, next to the others. Sam had still been sleeping a moment ago when he'd brought the first load in, but now, Sam pushed himself up out of his bed and was rubbing his eyes with the back of his hand as he watched Dean.

After a couple more hours of driving last night, they'd decided to stop and spend the rest of the night in a motel. But Dean hadn't forgotten what he and Sam had decided last night, so he'd woken up early to go pick up a few things. There were upsides to only needing four hours of sleep.

There were also upsides to dating someone who'd become completely obsessed with sleeping in. It was probably because he hadn't been able to sleep for the first few millenniums of his existence, so he had a lot of catching up to do, but Cas had gotten downright lazy since his fall. Now, though, it meant that Cas was still passed out in the bed that he and Dean had shared last night, and showed no sign of moving any time soon.

"Seriously, though," Sam said, as he pushed himself to his feet and started digging through one of the bags. "Did you buy out an entire party store or something?"

"Oh, come on, I didn't buy that much," Dean protested. Sam just raised one eyebrow, and Dean amended, "Okay, fine, I did. But Cas has never had one of these before, I want it to be good."

Sam just laughed and pulled out some of the decorations that he had bought. The angel stickers got a snort and a "Seriously, Dean?" before being set to the side. Then he pulled out a couple of the banners that Dean had bought, and immediately lost it. "Really?" he asked through his laughter, holding up the banners for Dean to see, even though he already knew which ones they were. The first one was bright blue, and had a picture of a cartoon stork holding a baby with the words CONGRATULATIONS, IT'S A BOY! written underneath it in bubble letters. The second was a softer blue, and declared this to be BABY'S FIRST BIRTHDAY!

Dean couldn't hold back a smirk, though he tried to play innocent. "What? It is his first birthday. Why shouldn't I get him a banner to celebrate?"

Sam shook his head and went back to digging through Dean's stuff. Dean looked over at his boyfriend – who was still completely buried under the blankets, somehow Sam's laughter hadn't woken him up – then pulled out the rolls of tape that he'd remembered to buy just in time. "Just quit complaining about the decorations and help me get this all set up before the birthday boy wakes up."

"Oh, I wasn't complaining," Sam said, completely serious. "Trust me, Cas is going to just love them. Especially the part where you called him your baby." That was as long as Sam managed to keep a straight face, and then the laughter broke through again.

Dean rolled his eye and tossed a thing of tape toward his brother. And if it happened to bounce off the side of his head because Sam didn't catch it in time, well, that wasn't Dean's fault. "Just shut up and tape," he said, then turned around to follow his own advice.

( )

Cas woke slowly the next morning, not wanting to open his eyes, and definitely not wanting to leave the warmth of his bed. He rolled over and awkwardly groped at the other side of his the bed, frowning when he realized that nothing was there. That meant that Dean must already be awake. Which meant that it was probably time for him to get up so that they could hit the road and try to reach the bunker before dark.

He didn't, though. Instead, he wrapped his arm around Dean's pillow – since he couldn't hold his actual boyfriend – and tried to drown out the sounds of Sam and Dean moving around the motel room.

The two of them were definitely moving around and laughing, more than they normally did first thing in the morning. Cas didn't dare open his eyes to see what was going on, though. The moment that the Winchesters realized he was awake, he'd be dragged out of bed and loaded into the car, and Cas definitely wasn't ready for that. He figured that if he had to sleep now, he might as well enjoy it as much as he could. Dean didn't seem to share his opinion.

So instead, Cas just listened as Sam and Dean bantered.

"You're side's too high," Dean snapped, and he must have hit his brother, because Sam gave a squawk of protest.

"Not my fault if you can't reach high enough," Sam said. "Go climb on a chair or something." There was a noise like paper crumbling, and then Sam added, "Bitch."

"Throwing things? Real mature, jerk."

There was a laugh, then a crash, and then Dean practically shouted, "Woah, woah, woah! See what you did, asshat?"

"You're the one who knocked the bag off the table!"

Dean growled, not sounding nearly as playful as he had just a moment before. "I swear, if you broke my pies, I will freakin' end you!"

That conversation was… confusing, to say the least. Cas' curiosity finally won out over his desire to feign sleep, and he sat up slowly, blinking and rubbing his eyes with the back of his hand. Then he looked around the room for the first time.

He blinked again, not quite comprehending the transformation that the room had undergone since they'd first checked in the night before.

Multicolored streamers hung from every surface, held in place with silver strips of duct tape. In parts, it looked like whoever had hung the decorations had attempted to do a good job, and had even made attempts at tying bows around the backs of the chairs. The majority of the room, however, looked as though a child had thrown random amounts of streamers everywhere they could, and hadn't cared about what the result had looked like. Either that, or whoever had hung them had simply done an extremely poor job.

The streamers were far from the only odd thing about the room, however. There were also balloons covering the floor, some with golden ribbons tied to them, some without. Someone had used ribbon to hang balloons upside-down from the ceiling fan, so that they hung down from the ceiling at about eye level. The table had been covered with a bright pink tablecloth that proclaimed this to be "The most totally awesome birthday ever!" in multiple different fonts, and there were a variety of banners that congratulated someone on having their first birthday.

Sam and Dean were over by the table. They had apparently been in the middle of hanging yet another banner – this one read "Happy Birthday" and had a blank space afterward, in which Dean had scribbled the word CAS in his almost-illegible handwriting. A brown paper grocery bag had clearly fallen off the table, and Dean was checking the contents with a worried expression on his face, while Sam grinned beside him. He had a balled-up grocery bag in his hands, and as Cas watched, he tossed it at Dean's head with a laugh.

Cas cleared his throat. "Dean?" he said slowly, making both men immediately look over at him. "Sam? What exactly is going on?"

Dean immediately straightened and scowled at his brother. "See what you did?" he demanded. "You woke the birthday boy."

Sam rolled his eyes. "I'm pretty sure that was your fault, Dean."

"Birthday boy?" Cas repeated, and his frown deepened. He felt as though he was even more confused than he had been just a moment ago, if that was even possible.

"Yeah," Dean said, and in an instant, his anger vanished, replaced with something that almost looked like pride. "You said that you'd never had one, and today is Thursday, so we figured, what the hell?" He grinned, and yes, he definitely was wearing a smug expression.

Cas opened his mouth, the closed it, not sure what to say. "Thank you," was what he finally settled on. "That is… That is very kind of you." And it was. Cas was used to the fact that Dean didn't always express affection in the small ways that Cas had seen other couples take part in, like hand holding and hugging each other in public during everyday life, instead of reserving their touch for important moments. Honestly, Cas would have thought that Dean was more likely to take a bullet to save Cas' life than to throw him a party – the thought of Dean throwing him a party had never even crossed Cas' mind for a moment – and discovering that he was wrong was nice, to say the least.

"And you remembered that I'm the angel of Thursday," Cas added after a moment.

"'Course I did," Dean said with a grin. Behind him, Sam coughed, hard enough that it made Cas turn to him in concern. Dean gave his a nasty look, then hurried to say, "I got something for you." He reached into one of the closest brown bags and pulled something out, then tossed it over at Cas. "Catch."

Cas did, and looked down at the item in his hand. It was a small tiara, with a fluffy pink lining running along the bottom and fake gems in a slightly-more-garish shade of pink.

"Seriously, Dean?" Sam asked.

"It's a birthday crown," Dean said, like that should be obvious. "Everyone's got to have a birthday crown!"

Cas frowned down at the plastic tiara, and had the undeniable feeling that Dean was mocking him somehow. However, it was nice of Dean to think of him, regardless of his motivations. And if Dean was being serious, then Cas didn't want to run the risk of accidentally behaving rudely.

So he placed the tiara on his head, using the ends of the comb to keep it in his hair. Then he turned to Dean and said, completely serious, "Thank you. I will cherish your gift."

Sam coughed again, and this time, it was a bit more obvious that he was trying to hide a laugh. Dean, for his part, was staring at Cas as though his reaction had been completely unexpected. He didn't laugh, though. Instead, he looked like Cas' reaction had pleased him more than he had expected it to.

"So, birthday boy," he said after a moment of silence, and walked over to that he could drop down onto the bed beside Cas. Then he grinned and threw one arm around Cas' shoulder, drawing him closer to his side as he added, "So, how do you want to celebrate?"