I've been trying to think of things you haven't listed yet! How about a list of good (but almost certainly under-reviewed) Castle crossovers with any show other than Firefly...? There must be some...
Here’s the crossover fandoms list.

seen from South Africa

seen from Philippines
seen from United Kingdom
seen from United Kingdom
seen from Germany
seen from United Kingdom
seen from Vietnam
seen from United States

seen from United Kingdom
seen from United States

seen from Australia

seen from Australia
seen from United States
seen from Malaysia

seen from Australia
seen from Poland
seen from Spain
seen from Australia
seen from Chile
seen from China
I've been trying to think of things you haven't listed yet! How about a list of good (but almost certainly under-reviewed) Castle crossovers with any show other than Firefly...? There must be some...
Here’s the crossover fandoms list.
Public Service Announcement
Hi y’all, long time no see! Katherine here, I’m your new admin (you may know me as @takeiteasykate or @klff_ at twitter or The-KLF on your choice of fanfiction website). It’s been a long old while since we had any posts here at the prompts blog, and we have a lot to catch up on.
First up, the admin change. Louise (@inkstainedcoffeecup) has been hit by a severe case of Real Life in the last 10 months, for which she has asked me to apologize to you all. I have stepped in to help out, with the caveat that I am also pretty damn busy! Hopefully I’ll be able to queue up posts on a weekend so it’s all going automagically through the week.
Most importantly, there are over 100 messages in the inbox. The queue will start some time this week, and I hope the awesome writers who are still being inspired by our great show find some new stories with these prompts! I’m excited!
Riddle: they left at night and arrived at the gas station at dawn. Where did they spend the night?
Sooo, it’s basically been forever since you prompted this, but I hope you like it!
Tellurian
An early season 5 ficlet
“Got everything?”
Broad palms patted at his chest, then his hips, moving ontohis back pockets in their survey for the essentials. “Phone, car keys,snacks. Yeah, I’m set. You?”
His companion smirked, lifting her arm to show him the throwblankets she’d stolen from the back of his couch. “Everything else is inthe car, right?”
“Right.”
She exhaled. “Then I’m ready. Let’s go.”
He made sure to leave the light on behind them, bathing theliving room in a welcoming glow.
She did another inspection of their things as they loadedthe rest into the trunk, lifting the bag of snacks and cocking an eyebrow inamusement.
“Funyuns, Castle?”
He shrugged. “They’re good. I bought the chips youlike, too. The garlic, basil, and olive oil ones.”
Beckett grinned. “Really not worrying about bad breathtonight, huh? I’m surprised.”
The keys slipped out of his hand, landing on the concretewith a clatter. “I – well – if we both have bad breath, it cancels out.You know this, Beckett.”
His partner snickered, returning the snacks to the car.“Whatever you say. Just tell me you at least packed water.”
Scooping the keychain off the ground, he nodded. “Ofcourse. I made some coffee, too. It’s in the thermos behind my seat.” Hemoved to the driver’s side, opening the door and lifting that bag to prove itto her.
Kate hummed, casting an appreciative glance his way. “Thinkingof everything, aren’t you?”
“Regular boy scout,” he quipped, waiting until sheclosed the trunk and moved to the passenger side to slide behind the wheel.
Beckett rolled her eyes, but her lips twitched upwardsanyway. “You were never a scout, remember?”
Delight rippled across his shoulders at her memory, therecollection of something he’d said to her on their first case together.“Honorary then,” he said. “I think I probably qualify for thatby now.”
She snorted, clicking her seat belt into place.“Whatever you say, buddy. I’ve admitted it was good thinking; no need toget cocky.”
“But I thought you liked it when I got co-”
“Castle,” she interrupted, barely sparing him aglance as she programmed their destination into the GPS on his dash.
“Right,” he said, glancing in his mirrors, waitinguntil she finished to back out of his parking space. “Getting on the road.Looks like we should make good time.”
Kate hummed an agreement, kicking off her shoes andsquirming to make herself comfortable as her hand fell to rest in the center ofthe console.
“Don’t jinx us,” she warned after the fact.
Thankfully, it seemed that he hadn’t spoken too soon, as thecity that never slept granted them a brief window where the traffic wasn’tmiserable. Still, he waited until they’d made it to the highway and pointed thecar upstate to take his partner’s hand and give it a gentle squeeze. They bothseemed to breathe a sigh of relief, of gratitude that everything seemed like itwas going to work out and the night would happen as they’d planned.
“You okay?” Kate asked a little while later,turning in the bucket seat to face him. “I can drive if you want.”
Castle shook his head, brushing his thumb over her knuckles.“I’m good to drive. Just glad the killers of New York made their dirtydeeds someone else’s problem tonight.”
“Me too,” she admitted, leaning across the consoleto brush her lips over his cheek. “But really? Dirty deeds? That’s onestep away from ‘dastardly,’ Castle.”
“Which is also a great word.”
“If this were Dudley Do-Right, maybe,” sheretorted, grinning against his chin.
Rick laughed, jostling her hand when she retreated to herseat. This was one of his favorite things about being with her, the fact thatthey could go back and forth like this without missing a beat.
“You mock the world’s most well-meaning Mountie,Beckett?”
“Oh, hush.”
She was still smiling, though. He could hear it in hervoice. And for that, he would suffer whatever teasing she wanted to dish outover his vocabulary.
“Anyway, I was merely expressing my appreciation forthe fact that we didn’t get called to a crime scene five minutes before youclocked out.”
His girlfriend gave his hand a patronizing little pat.“Yes, yes you were. By quoting a 1960s cartoon.”
Turning his head just a tad, he stuck his tongue out at her.
“There are better uses for that tongue of yours,Castle,” she drawled, slipping her fingers up his arm. The touch sent ashiver through his limbs, and his blood warmed in anticipation.
“No fair, doing that while I’m driving,” heargued, easing off the gas as the slowpoke ahead of them decelerated even more.
Kate hummed, swiping her thumb along the inside of hiswrist. This time, though, it was hypnotic and soothing instead of arousing.Okay, a little arousing, too, but that was true for most of the things Kate Beckettdid.
“GPS says we should be there in a couple of hours,”Beckett started once he’d passed the slow driver, glancing behind them to checkout the vehicle. “Plenty of time to do it when we arrive.”
Beckett’s back in uniform.
Submitted by @takeiteasykate :-)
Hi y’all
Thanks for sending in so many new prompts, it’s really great to see your ideas! I have a small request though: if you know you sent an ask with a prompt, but don’t see it posted yet, please don’t resend the prompt. It will come out in the queue eventually (we’re only posting a couple of times a day at the moment, and there’s at least a couple of weeks’ worth in the queue right now), so please be patient!
Thanks! -K
:) On behalf of Tricia, who doesn't do tumblr: Is there a fanfic of a bored Beckett pretending to be a muscovite at the Glechik cafe?
So far I’ve found one, femslash with Beckett and Natasha Romanov, called “Speaking In Foreign Tongues”, by Rainne. Will keep looking.
Sorry for the mini hiatus, y'all. Life kicked me again.
I've queued everything that was in the inbox and they'll come out twice a day as usual.
With the recent decision by Tumblr to censor the entire site I'm pretty ambivalent about sticking around, but I do plan to download this blog and try to find somewhere else to host it (or archive at the very least). Of course you will be the first to hear when that happens 😊
Sorry for the mini hiatus, y'all! Life kicked me again.
I've queued up everything that was in the inbox and they'll come out twice a day as usual.
With the recent decision by Tumblr to censor the whole site, I'm pretty ambivalent about using it ever again, so it may be that not many more asks will be queued. I'm going to download the blog and attempt to restart it somewhere else (or at least archive it), and if I manage that of course I'll let everyone know.