There’s a lot out there on utilizing ideas from other media in game sessions. Borrow plot and stick it in a new genre, adapt a character’s overall profile to the world you’re running in, so on and so forth.
And then there’s the tendency of a game group to do the same thing. After all, a tight-knit group stays that way in large part because they’ve got a lot in common; they’ve probably seen the same shows or movies (and if not, might be fixing that after session or if the GM’s got block), they’re likely loaning each other’s books, and if they’re playing in multiple games together… well. It’s pretty much inevitable that someone’s going to find inspiration, and everyone else is going to jump on it.
When it actively breaks character or immersion, particularly when immersion is a Big Element, then yes, this can be a tad obnoxious. If the metaphysics just don’t work with the references, if they won’t stay safely OOC, if the overall drift of the session is rapidly turning into “Let’s see how many jokes we can throw in” on both sides of the Fourth Wall rather than focusing on the plot IC and the jokes OOC, if what’s being tossed in is a carbon copy of the source material and that’s supposed to be its main redeeming factor/selling point, or even if they’re referencing another game which for Reasons you’re both not involved in and generally annoyed by—then yeah, this is a pain in the neck.
On the other hand, if they aren’t being obnoxious about it, the best response to transplanting really isn’t to smack it down at the first available opportunity. I recognize that it can be a bit frustrating feeling as if your work is being somewhat overshadowed by The Lastest Amusing Thing, but unless it really needs fighting, there’s no reason to waste your energy fighting it when it can work to your favor.
After all, if there’s something they all find nifty—check it out, that’s something you know you’ll get a good reaction from. The entire party grins every time somebody attacks a zombie with a Wand of Cure Light Wounds/torch/staff/broken javelin/whatever because they’re poking undead with sticks (even the one who hates fighting undead things)? When providing the next round of undead, make sure that somewhere on the battlefield is a tactically useful stick. Instant crowd-pleaser. As long as it wouldn’t break your story, why not?
It might get them through block, particularly if they’re the kinds of people who can pull it off—managing to adapt the concept without just taking the whole reference with only the vaguest nods towards modifcation. I’ve had to resort to inspiration-by-transplanting a few times; for instance, after a short deadline and about a week of block, I ended up at one point basing a build around an extended Secret of Kells reference with a backstory inspired by the second Dragonbreath book, and she turned out to be one of my better characters once we got over the usual “it’s the beginning of the game, I hate this one already” hump.
And if you have the kind of mild style clash that manages to sour the game without being a full dealbreaker, a group with a tendency to transplant or reference can use that as a way of working around the clash. Think of it as a coping mechanism.
So—yeah, transplanting may not be the best of tactics, but when it’s done in moderation, it’s better to encourage it than to smack it down. Much more inspiration and synergy that way.