A Study In Emerald, by none other than Neil “and then they all died” Gaiman, is something that many said could never be done: a Sherlock Holmes/HP Lovecraft crossover. I am not much for the fanfic in either of those fandoms, so I hope you will understand my full meaning when I say that it’s also, as of this posting, tying in first place for Best Fanfic I Have Ever Read. It’s amazing. I wrote a long, spoilery review thing here, I loved it so. It’s everything the best fanfic should be; it’s funny, it’s amazingly written, and best of all, it tells you so much about both canons while being entirely its own thing. Even if you’ve never read any Conan Doyle or Lovecraft, then you should, simply so that you will be able to appreciate this fanfic. It won’t take long - you want Study in Scarlet, The Final Problem, The Empty House, and Call of Cthulu, but that’s it. It’s all for free online, too. Go on. You won’t regret it.
(And if you do, I promise to send you cookies or something. That’s how confident I am, people.)
Daemonology by trinityofone is a Stargate:Atlantis/His Dark Materials crossover fic of joy. Even if you’ve never read His Dark Materials, because while obviously you should, like, right now, the author has kindly provided a cheat sheet so even you, poor deprived soul, can appreciate this fic. Because it’s just that good. This is one of the ideas that should never work, but then in the right hands it does, and is all the better for it. This is definitely helped here, though, by the fact it’s less a strict crossover and more a…fusion, a binding of the universes, rather than something like “Lyra and Will go to Atlantis”. It’s simply beautiful; heartbreaking and funny and cute and perfect, all at once. It combines the best things from both canons amazingly. It’s true, in the way that the best literature is, the way His Dark Materials is, and I can give it no higher praise than that.
Change is the Only Constant by marag. This crosses over House with the DC universe. I hate to say it, because it sounds not just bad but impossible. However, it’s true, and getting that out immediately is probably best. Because people, if you know anything about either fandom, you don’t want to miss this. It’s not often you can say this about crossovers, and certainly not about House and Batman, but… this makes so much sense. It explains both worlds – especially some of the crazier plotlines in the DCU – so much better than the canon did. It’s amazing, in all senses of the word. Plus, this time it really is vasculitis, and that just makes me happy. Hee.
The Gargantuan Garden by yahtzee63 is Series of Unfortunate Events crossed with Edward Scissorhands. (I am so glad at this point that it’s gen, because the alternative is kind of brain-breaking.) It’s one of those things that is tiny and weirdly perfect because it makes such a perfectly bizarre kind of sense. One of those things that makes me see the sadness of both canons in a new way, while also imparting a weird sense of hope. It's very quiet, and simply lovely, a bit like sitting and watching the rain fall on the rolling hills.
Where Did All The Physics Go? by amireal is an Atlantis crossover with… a fandom that the author would rather not be revealed in advance. All you need to know is that basically anybody will be able to read this and share in its cracktastic joy. It’s especially notable for the hilarity of the characters responses to, er, the crossing over. I was just vastly, vastly amused the whole way through, especially by the Zelenka. HEE.
Thospar by scrunchy is another of the sga_fusion-inspired fics, but like the His Dark Materials one, it too manages to combine the two canons involved in a refreshing and wonderful way. In this case, that would be Stargate: Atlantis and, ah, Sports Night, the sort-of sitcom about a sports wrap-up show that Aaron Sorkin did before The West Wing. It turns out that the result of this mix is frothy, delightful and overly caffienated; it’s a joy, seriously. You’ll need to see Sports Night to appreciate it, because a lot of the joy comes from the canonical references, but once you have, well: say hi to Lt. Hurley, Dr Goodwin, and Majors McCall and Rydell. We even get a happy side-order of the traditional Atlantis crew as well, because we’re lucky that way.
Vindication by Calypso (who I think is mzcalypso, but am willing to be corrected). This is the archetypal Horatio Hornblower crossover: sheer revisionism in which [x character from another fandom] turns up and makes sure that the Incident In The West Indies That Shalt Not Be Spoke Of doesn’t end the way it does in canon. In this case, it’s Stephen Maturin from the Master and Commander books. But while that sounds cheesy… this, here, is more or less why those stories exist. It is the Plato’s Form of revisionism, if you like. It is wonderful, and OK, yes, dammit I wish this had happened instead. But with this fic, I want that just as much for the lovely Maturin snark as for the end result, and that’s saying a lot.