These would be random cameos, references to fantasy or science fiction stories, themes or concepts (kinks?) that make regular appearances? What random things appear in your writing? A few of mine: 1. Because I am terrible, I occasionally cameo characters. Daniel Jackson (Or his ancestor since the story was set in the late 1930s) makes an appearance in a Chrono Crusade fanfic. I have also stuck Shiro in a homestuck fic I'm writing. 2. I make references to science fiction and fantasy in almost all of my writing. These might be stories the character has read (I try to make sure it's accurate to the time period) I occasionally use technology native to other fiction universes. (Voltron is getting ansibles at some point in time. Homestuck got the atevi security wires because electric death sounds like a troll security method.) 3. Snarky historical notes are occasionally a thing. Snarky notes in general are occasionally a thing. There are other things, but I can't think of them right now.
Gah, I'm mostly drawing a blank now, even though I know I've done the thing, but I do remember that I had one homestuck fanfic where a helmsman watches a movie that's meant to be 2001: A Space Odyssey (because HAL), and iirc, the troll movie title referenced the 'Daisy, Daisy' song part as 'a humorous musical number.' And also paging @coldstars, who had the brilliant idea of porting troll naming conventions over into the transformers universe, which made me laugh out loud the first time I saw it.
i like to reference a lot of media in my stuff, but that doesn't seem all that surprising given that i write for homestuck, heh. i know i've vaguely referenced interview with a vampire in one of my fics?
I write Dragon Age fanfic, and Draon Age is one of those things that encourages you to make a lot of original characters. I, at least, have like twenty five of them for different worldstates and playthroughs, but only one specific set of them is my "canon" timeline, so... The others make cameos. My Brosca warden, Glitter, in my canon has actually escaped to Orlais and is currently making out with her gf Petra Cadash on top of a giant pile of money they scammed from the nobles. I also use a lot of direct translations of Brazilian idioms in my Dalish dialogue. It's an easy way to make Dalish dialect Common sound weird for native speakers. The occasional reference to Brazilian literature also slips, like a character saying that a particular minstrel, who is pretty Parnassian, sounds like a frog - it's a reference to the Manuel Bandeira poem "Os Sapos".
The character Salbrakmuir or the Vagrant crop up as offhand mentions. Or, if applicable, a certain alien with four horns, four eyes, four arms, computer cord hair, a coffee travel mug, and a shirt with some stupid phrase in HEX. A recurring theme is parental abandonment and parental emotional neglect. Took a while for me to realize why. Solitude, and how to deal with it. (Or how not to deal with it. Looking at you, Jhenya.)
Homestuck and horrorterrors, mind control and memes 8) I also bring in themes from Sacrifices Arc and other fanfiction I've read over the years, because I don't know how to stop making allusions and references
I tend to re-use characters in my original fiction. I have so many characters so it's kind of hard to notice, but most of my background characters are main characters in another story. It's fun. I do the same thing with fanfiction. Need background characters? Steal them from another series.
I'm rewriting mine and my BF's old PPC characters to be a thing in a gaslamp fantasy world I'm building. Among other things, the mutated fox is now a nogitsune and the Enfant Terrible now has a legitimate disorder instead of my teenage conviction that violent six-year-olds are inherently funny.
I'm very prone to "eyes that change color or glow for Significant Magic Reasons and have a lot of attention drawn to them" (which is pretty funny, since I pretty much never notice people's eye colors IRL) and "character with magic powers activates them unconsciously when angry or upset, causing harmless but visible effects." Do those count?
I referenced the lioness quartet in a magic the gathering fanfic. because fuck it, that's a good story and I could think of ways to adapt it.
The number one thing that shows up in my writing is cuddling and/or falling asleep together. I've known that for a while, but I only realized recently that another concept I keep coming back to is bodysharing, both when I'm reading and when I'm writing. Not sure why it interests me so much, but I'm inclined to blame the Bartimaeus Trilogy.
i've used the names (first or last, never both together) of friends in my fics many times. usually for one-off mentions or background characters, but i still like doing it. on a more personal level... every single fic i've ever written with any level of eroticism has included hair touching. but then again, every erotic encounter i've had IRL has involved hair touching. I LIKE HAIR OK.
When I need to name an OC in a fanfic (which is like…never because OCs in fanfic is something I Just Don't Do unless they're background characters or more frequently dead bodies) I almost invariably swipe a name from another fandom. For some reason doing that makes me happy, I dunno.