Hello! This was originally started back in Season 4, when we found out Adam Baldwin would be guest starring on Castle. I was extremely excited as a Firefly and Chuck fan. I thought it would be pretty great if Casey walked in and, being Casey, decided Gates and her "sir" wasn't worth his time. Then it turned into me loving Caskett and Charah and not being able to go without it, so throwing that in too. It's mostly written because I like crossovers, and these shows.

Plot importance: Chuck, somewhere in Season 4, because they're still in the CIA. Castle, Season 5, before Murder, He Wrote.

A tall, scowling man walks through the doors of the 12th precinct, accompanied by 2 others. All three are wearing black business-wear and the frontman wearing sunglasses.

When given curious looks and asked their purpose at the main floor, all that's required is a flash of their badges to gain entrance. They ride the elevator to the detectives' bullpen, scanning the floor and acquiring their objective.

As they begin walking, however, they are stopped by a woman in a business suit.

"Excuse me, but who do you think you are?" She barks at them. "I am the captain of this precinct, and I don't know who the hell let you up here, but I will be glad to have my officers escort you back down."

She can't see his eyes, but she sees what resembles a smirk grace the tallest one's mouth. He does nothing but something of a grunt and walks on by, the other 2 following behind, sharing a knowing look.

She never looses pace, finding them going to a specific desk. Detective Beckett's.

Beckett is there with her tag-along and possibly-something-more, Rick Castle. They're both examining the board with care, occasionally writing notes as more information comes in. The current case is a rough one. No ID and a clean kill. It's all too perfect for anyone's liking.

Castle's eyes go wide with excitement like a child's on Christmas. Anyone could tell that he was going towards CIA, NSA, cover-up theories. Beckett just stands from her chair and looks the 'leader' in the eyes.

"Detective Beckett-" The man starts, but never gets to continue.

"There will be no talking to my people without going through me, and that's an order." 'Iron' Gates is already shaken from being passed over, laughed at even. She glares at both Castle and Beckett not to say a word.

"Ma'am, I have direct orders to speak to them without interference from unneeded assistance, so can it." The leader snaps at Gates and turns back to Beckett.

"Colonel John Casey, NSA." Casey removes the glasses from his face. "This is Agent Sarah Walker and Agent Charles Carmichael, CIA, and my team."

Chuck gives a miffed look at the back of Casey's head at the mention of 'his team', but leaves it be.

"We're here because the case you're currently handling is being transferred to the CIA and NSA. You'll need to file a full report with all your information on this case, and understand pursuing any and all leads will be going against the Federal Government."

"And, why, exactly is this case being taken over?" Kate did not enjoy sharing her cases, let alone just letting them go.

"That's classified information." Sarah says, flicking her eyes to the murder board. "We've been asked to handle this as a precaution. Let's just say the wrong people are involved, and we want no danger to come to anyone here."

"It's Sir, to you, and there will be no transferring of anything in this precinct without my express permission!" Gates growls, invading Casey's personal space.

Chuck and Sarah share a look of worry, but Casey seemingly doesn't take this woman's threats too seriously. Then the other two pipe up.

"And I'm not just giving up my case to some group of random agents in suits, claiming to be from the government!" Beckett glares at the three, and eventually Castle, as he is almost bursting with giggles over the entire situation.

Chuck jumps in quickly, "Look, uh, why don't you just talk to our general, General Beckman? We have agent-y things to do, you've got murders to handle, and unfortunately, our paths have unhappily crossed here."

Sarah pulls Gates aside and directs them to the Captain's office, but not without a parting glare to continue the argument with Casey.

"Do you know a Detective Slaughter? Related, maybe?" Castle pops out, much to Beckett's chagrin of the entire event. "I could swear, you look just like him. Even act like him!"

Casey rolls his eyes and doesn't even bother to answer the writer's question. Castle can be the detective's moron, he's already got Chuck to deal with.

"Do you get to go on missions? Fight villains? Crawl through vents? Walk away from cool explo-" Chuck's pretty sure this guy is trying to name every spy trope in the book (which, admittedly, he can say he's done most or even all of.) when Castle suddenly snaps his jaw shut. Beckett has her hand resting on Castle's shoulder, and a look is shared, and a quiet "Sorry.." is mumbled. Chuck's reminded of himself and Sarah, and the numerous times only a touch was needed, and can guess what's going on there. He doesn't comment. Doesn't want to ruin their moment. He thinks Casey might actually gag or give his grunt of 'there is a line to how much couple crap I can take without wanting to shoot something'.

Gates is annoyed, but Sarah gives him a satisfied smile as they return.

"Pack up everything for the agents, and file your report. I know you won't like it Detective Beckett, but leave the case alone. There will be others."

Beckett almost protests, but the look in Gates' eyes looks serious, and she's not up to fighting it right now.

So they pack up the case files in mutual silence until Castle eventually pulls Chuck over to ask "So, the blonde, Walker, agree with me here. Great to date a sexy woman of the law, isn't it?"

Castle's grinning like a maniac, and however he deduced Chuck and Sarah were together, he has, and Chuck finds no harm in answering.

"Yeah, sure is." Sarah gives him a questioning look at the sudden puppy eyes he's making, but Chuck smiles thoughtfully anyway. "We're lucky. We're a team and a relationship team. So, what about you two?" Chuck eyes at Beckett quickly, and Castle goes from smiling to a little shocked.

"Are we that obvious?"

"You work with a room full of cops and you don't think a CIA agent can pick up on that?"

Castle shrugs, and leaves it be, returning to find Beckett has finished the task without much of his help needed.

"Sorry about Gates, she can be a bit harsh." Beckett says, handing a box of files and collected evidence to Casey.

"Compared to our general, she's tame." Sarah says and the other men give slight, but caring nods of agreement.

"Thank you for your assistance, Detective Beckett," Casey grimaces. "Mr. Castle."

"Come back anytime, I'd love to incorporate a spy element to my murder mysteries. I'd love some inspiration."

Castle is full of cheer in saying this, but Casey grunts, Sarah roles her eyes at Casey, and Chuck smiles back and nods, thinking about how awesome it would be to be a muse, of all things.

Thanks for reading! Hope you enjoyed, let me know what you thought! More Chuck and Castle are always needed.