OMG! Anon, you do not know how happy this ask made me 😀 … but also, very conflicted. Because–just one? How could I possibly choose? O_O
I guess it depends on how you mean by “crossover.”
Like… the DoS world and a different world are actually the same (via different continents or time travel, perhaps)? Or take the characters of DoS and transplant them into a different world (aka a “fusion” as I call them)? Or even, keeping in mind how many derivative fanfiction of “the second reincarnations of Shikako Nara,” in which world would I choose to have her reincarnate yet again? (Also, I’m assuming you’re not including the canon Naruto world…)
So, just to cover all my bases, I’m going to answer ALL THREE! And three times over at that! 
—
1) Crossover worlds (same universe)
In no particular order, the three fandoms I would choose as crossovers are: Star Wars, Final Fantasy VII, and Akagami no Shirayukihime. Why? Well… because in my mind each of them have different ways to be within the same universe–now whether or not that means the characters of DoS actually meet the characters of the other worlds would depend on what kind of story I’m going for.
With Star Wars, at first I thought it would be absolutely thrilling to Shikako to realize that the Naruto world was in the same universe (specifically, the same far far away galaxy) as the movies from which her beloved lightsaber originated. But then the more I thought about it–when in the Star Wars timeline this is, would make Shikako absolutely horrified.
Because it’s one thing to help prevent the (many numerous) excess deaths of certain people–essentially tweaking canon to be a little bit better–but it’s another thing entirely to… let’s say… prevent Anakin Skywalker from turning to the dark side. Not that that’s necessarily the storyline I would go for, but it would up the stress levels to ridiculous levels.
Of course… now that I think about it even more, it’s far more likely that all the shinobi in the Naruto world would be considered Sith which would make the Jedi (or at least, some Jedi) question what exactly is good and evil, etc.
I’m cheating a little bit with the FFVII decision, only because I’ve explored this crossover before in my FFVII series, “Into Thin Air,” with my own SI!OC character Windy Strife, but the reasoning remains the same. There’s something about both fandoms’ mythology which almost resonates with each other and makes it seem like they are the same world but maybe a few millennia apart.
In my “Into Thin Air” series, I have the Naruto world being the distant future of the FFVII world with my SI!OC somehow being summoned and mistaken for a Namikaze. I also greatly hint at Kaguya being a remnant of Jenova. For a DoS crossover, however, I think I would still have FFVII being the past but… I think Kaguya would actually be a sort of failed Ancient 2.0? (For those of you who don’t know–in FFVII there is a race of basically Tolkien’s elves but by the main game, there is only one left aka Aerith and she dies before the game ends so…)
Like… the giant tree with the chakra fruit is meant to be the Planet bestowing Ancient powers onto whomever eats it to restart the Ancient race but the Planet has been showed to be pretty bad at judging things? So it’s no wonder why Kaguya went berserk. It also draws parallels between the bijuu and WEAPONs which, as far as I understood, was the Planet creating giant monsters to defend itself from humanity.
Unsure how exactly Shikako would get involved with this all? I’m thinking most likely Gelel–because that’s the only thing that she would have had that no one else has had access to and which her reincarnation from “our world” doesn’t explain. So the Gelel stones were probably derivatives of materia (FFVII magic stones), and the voices of Gelel speaking to Shikako during her possession were actually probably the original Ancients.
Okay so, now that I type it out, the plot I would most likely go for is that Kaguya was meant to be Ancient 2.0, which backfired horribly, and Shikako gradually becomes Ancient 3.0 via exposure to her Gelel stone. So the Planet is urging Shikako to, basically, clean up their mistake (of Kaguya). Which, she was going to do anyway? But there’s some resistance because Shikako doesn’t appreciate being told what to do 😡
Akagami no Shirayukihime is now an anime! 😀 I primarily know it through the manga–but either way, it’s super cute. For this crossover, I do actually see the characters interacting with each other more directly. The lands/kingdoms mentioned in AnS would probably be a different continent than the Elemental Nations but still the same world and point in time.
Given the lack of world-ending melodrama in AnS, this crossover would probably be the most mild. As in, it would at most be similar to one of the filler episode missions that take up maybe two or three chapters and ends with no one almost dying or grievously injured. Frankly, the shinobi are just too strong for it to be a matter of battling between the two worlds, so the crossover plot would probably be something more political.
—
2) Fusion worlds (transplanted characters)
In no particular order, the three fandoms I would choose as fusions are: Katekyo Hitman Reborn, Harry Potter, and the DC universe. Mostly because they aren’t as compatible as the previous three fandoms with the Naruto world, but I do like the world structures inherent or at least implied in each.
So KHR is about a “normal kid” who turns out to be heir to a mafia famiglia in a world where organized crime also sort of has magic “Flames” based on the rainbow? Sort of. With this one, I would actually consider doing both a fusion and a crossover–in the sense that the characters of DoS are transplanted into the KHR world but they also get to meet the KHR characters. I think I’ve seen a fanart which kind of… let me see if I can find it… HERE IT IS! OMG, it’s been many a moon since I’ve seen this, but the bare bones of the idea still fits. The KHR characters would make a cameo but they wouldn’t necessarily be vital to the story line so…
So Tsuna, the main character of KHR, is the Juudaime of the Vongola Famiglia and I would have the DoS characters be yakuza members–in that similarly odd way that the mafia works in this world. Probably the Hokage position (and doesn’t that name work well given the magical Flames) is not actually the head of the yakuza so much as a Champion?
I guess it would be… the Clans of Konoha are actually separate yakuza clans, but they are all subject to the Hokage. Except there isn’t always a Hokage? Like… there are a series of challenges which a person must undergo in order to become Hokage–and each one corresponds a different Flame type/clan. Obviously, Naruto’s goal is to become the next Hokage and the various Konoha Twelve are his Guardians.
The Harry Potter series, as most everyone knows, is a fascinating world which is hindered by the titular character’s lack of knowledge of the world. While I have done a series of character analyses for which DoS characters would go in which Hogwarts House, I wouldn’t actually put them in Hogwarts. Given that… well… they are not British so why would they? And this would be an interesting exercise in adapting the Naruto world into the HP world.
Right off the bat, you have who are “pure-bloods” and “muggle-borns” being clan members versus non-clan. You can actually go further and do something like… Neji is a half-blood while Hinata is a pure-blood which makes his skill all the more damning for her. I dunno, something like that. I’m not sure what the storyline would be here, though? Beyond just, again, adapting the DoS/Naruto plot into the HP world.
DC universe, again, is an interesting world that suffers from its US-centric POV. Mostly it’s just an excuse for superpower AU which, again, would be fun to adapt. Take the clan specialties and crank them up into full-blown superpowers.
Actually, the plot for this one comes easier to me–probably something like… the Konoha Twelve have to form a sort of Teen Titans to take down Orochimaru/Akatsuki/Madara. Or… maybe something like… Ra’s al Ghul takes one of the Big Bad’s place and you get some character crossover from DC as well–most likely Tim Drake (because he’s my favorite) and the other Bat family. OR maybe the League of Assassins aren’t just nameless cannon fodder and are in fact the shinobi of Konoha, but some members (basically, the Konoha Twelve) rebel against him–basically taking Danzo’s place?
Hm… 
—
3) Reincarnated worlds
In no particular order, the three fandoms I would choose for Shikako’s second reincarnation are: the Tolkien universe, A Song of Ice and Fire (the Game of Thrones books, not the TV series), and… hm… it’s actually a bit of a toss up between Pokemon and Inuyasha. This is going with the same sort of set up of other recursive fanfiction in which Shikako has been reincarnated, yet again, into a different world by herself and a strange mixture of trauma and yearning for the DoS world. These worlds, though completely different from each other, all have an almost alien sociocultural mindset that forces Shikako to get some closure in one way or another.
Tolkien straight up has humanity not even the most important sentient race in his universe–hobbits are apparently where it’s at. Which I would actually have Shikako be–and, trying to hold on to her DoS roots, she’d try to be some kind of deer herder. Odd, but not that bad since she’d probably be a Brandybuck or a Took… or maybe a Proudfoot? I don’t think any of the LotR hobbits are from the Proudfoot clan and I wouldn’t want to overlap much… Either way, one of the genteel families so she’s forgiven for being a bit odd.
Of course, then Gandalf comes along and either whisks away Bilbo Baggins or Frodo, Samwise, Merry, and Pippin and she’s just like: “No, these hobbits have no idea what kind of madness lays in store for them–I can’t let this happen,” and she goes along with them.
In Tolkien universe, regardless of which fellowship she’s part of, Shikako slowly integrates herself into the group and finally… not lets go of her DoS life, but comes to accept the loss.
ASoIaF will go in the complete opposite direction–I mean, the Tolkien one would still require Shikako to use her shinobi skills, but she is very much so just acting as a bodyguard for her fellow hobbits–here she has to actively embrace her ruthless side. Not even necessarily her training as a ninja but the constant lying by omission; she has to use every bit of her DoS earned cunning to not only survive but enact justice for her Family. Because, let’s be real, she’d be a Baratheon. Not sure which Baratheon, but definitely a Baratheon.
I’m actually guessing she’d be one of Robert’s bastards but, like Edric Storm, a noble-born, and definitely one of the older ones–maybe around Gendry’s age… Like–Cersei would definitely want to keep an eye on her as the oldest Baratheon noble born heir, but not necessarily consider her a valid threat. Unsure if she’d be in King’s Landing or not (and held semi-hostage like Sansa) or, instead, sent to the Westerlands or… actually. That might be best? Because then it’d be hilarious if Shikako has to rely on the Iron Island pirates to get her out of there.
ASoIaF will definitely make her miss DoS even more–especially the relationships she made, her family and her teammates and her friends–but she also has to let go of those memories not out of any healthy reason but sort of out of shame. Because she’s no longer the “Shikako Nara” that those precious people of hers knew and loved–she’s a Baratheon, and she’s playing the Game of Thrones (the thing is, she doesn’t even want to be queen–she just doesn’t want the Lannisters to win).
Pokemon and Inuyasha, despite being very different worlds, both have a wishing component. In either world, Shikako is trying to find the wishing component in hopes to return to her DoS life. Obviously, that’s not how it turns out in either world, but that’s what she aims for at first. In both she starts off very much so as an animal preferring loner–much like in her Tolkien incarnation–it’s not that she’s bad at human interaction it’s just that, in her mind, she doesn’t want anyone to erase her past relationships.
In Pokemon she’s known as a legendary hunter (not in a hunt and kill way, but more like a storm chasing way) and she contracts with the laboratories. Unsurprisingly she runs into Ash/Satoshi (because I’m pretty sure he has literally met every single legendary) and ~somehow~ realizes that she can’t really go back. She can only go forward. (Or probably even Pokemon who are gods in this world can’t reverse reincarnation).
In Inuyasha… well. Frankly, I’d like her to have been reincarnated into the “present day” and think it’s just the normal world, then be completely blindsided by the Feudal Era demon nonsense, but I guess that takes away from Kagome’s story. I’m unsure, then, who Shikako should be instead. But regardless, she wants the Shikon no Tama, actually realizes that it’s more ofa monkey’s paw than a legit wishing tool, and commits to helping the group take down Naraku (and doesn’t his name offend her).
~
A/N: Anon, I hope this giant sprawling mess was entertaining for you. It certainly was fun for me–it took me several hours, hence why it’s after midnight.
JackSGreyson Says 