Depends on what you’d define as “anything”. There’s a lot of message board chatter, a lot of speculation, and a lot of situations where a board member has a third cousin of a friend has a step-sister who was once roommates with one hair and makeup girl who knows one of the makeup artists that work on Castle who said _______ [insert your sentence of choice here]. It’s nothing official, and in those situations I’d be hesitant to call it even substantial. In the general sense, the people who run around saying that sort of stuff are usually either looking to stir up drama or trying to figure out why they no longer talk to each other via social media/do interviews together etc.
Yeah, its kind of a weird thing, but for as many conspiracy theories as people could concoct, there are also plausible explanations for the change. I’m not going to get into all of them because, frankly, the larger question is why does it matter? I know people want their television ship to get along and be besties (some of them even want to ship them in real life), but there’s nothing written in their contracts that states Stana Katic and Nathan Fillion have to be the best of friends.
I get along with my co-workers when I’m in the office, we’ll laugh, we have a good time and whatever, but I don’t seek them out to talk after hours or hang out with them when I’m not at work. Some people do that, but some people are just content to do their jobs , go home, and socialize with the people they don’t see for 80 hours a week. And, after seven years together, I’d personally be kind of tired of talking to them all the time. They spend more time together working than they do with their families, so this concept that they need to praise/interact on social media or talk one another up all the time is just nuts to me.
Even if they don’t get along, it doesn’t matter. Their job is to bring two characters to life on screen and to make you love those characters and feel that story. There are people out there who believe that whatever supposed personal split took place (I think the general assumption is season five) negatively affected their acting, but I’ve got a whole blog full of gifs that really prove that sentiment wrong. Season five had some clunky, awkward writing that they struggled to sell, but season six and, especially, season seven prove that any percieved dislike between the two of them has never actually affected the acting. Stana and Nathan are professionals, they are still doing their jobs and doing them well. Whatever their personal feelings are towards one another; be they good or bad, is none of our business.