Fangirl authors, when writing scenes containing multiple characters it may help to remember the following simple equation:

4 Characters + 1 Character = 5 Characters.

It does not equal zero plus the two characters you want to see get it on; it does not equal zero plus the bad guy and the designated Hero of the Hour; and it definitely does not equal zero plus your Mary Sue. It adds up to five characters being present and you, as the author of the piece, have to keep track of every last one of them.

Failing to keep track of your cast in scenes involving several characters is, to my mind, one of the hallmarks of bad writing.

Let's say for the sake of an argument that a fanficcer wishes to add a new character to a scene which already contained four others. That's a lot of people to keep track of, but if the author don't at least try to keep track of them they're setting themselves up for problems. If there were four characters in a scene when it starts and none of them have got up and left for whatever reason, a newcomer brings the total of people present in that scene up to five. No matter how important that it is the newcomer bond with one character out of the original four in particular, he still has three friends with him, they are still going to have opinions on what they are seeing, and they are still going to make their various presences felt. Or they would do if the writing was even vaguely realistic.

There are any number of fan works out there - and often these are Mary Sue fanfics, though this can also be a problem when authors are writing about their own favorites - that give the impression that as soon as Character A shows their face, the rest of the characters might just as well have knocked off for lunch as continue to hang around waiting for the narrative to acknowledge their existence. Okay, so Ravyn McSue is bonding with her Designated Love Interest (or Joe and Jane are arguing about their relationship, or Vincent Grimdark is angsting about his tragic past: pick your poison), but what are the rest of the cast - who we must presume are still there because they were two paragraphs ago and there's nothing to suggest they've left - doing while all this is going on?

Okay, the point of the scene is that Joe and Jane are on the rocks and their behavior and reactions are clearly more important in terms of the narrative than that of any onlookers. The issue isn't that their reactions shouldn't take precedence - it's that accepting that one character's reaction is more significant doesn't mean the rest of the cast won't react at all to what they're seeing. By choosing to have them argue in front of Tom, Dick and Harry the author then makes themselves responsible for mentioning what Tom, Dick and Harry think about all this.

If a fic ignores them so completely they look as if they're more likely to be picking lint off their pockets or playing Snake on their cellphones than actually trying to contribute in any way at all, the author has lost track of their characters.

This is bad enough writing when the entire point of a scene is 'the regulars meet a strange young girl' or 'Joe and Jane have a bust-up'. It gets even worse when the purpose of the scene is not, in fact, two characters hooking up or falling out but actually a confrontation at gunpoint.

I have seen any number of supposedly dramatic scenes in bad fanfics where, in order for the author's personal favorite - OC or otherwise - to shine, the rest of the characters have to be written as barely-engaged dullards who don't seem to have the first idea that anything out the ordinary is actually taking place. The author's pet and the bad guy are having a tense stand-off, while the rest of the cast hang around in the background filling out crosswords or picking their teeth. Occasionally they may look up to remark upon some development or another before lapsing back into stultifying apathy, sometimes they just stand around and wait for the fight to be over, never mind that any or all of them should have been quite capable of helping out somehow.

Take this summary of a confrontation from a Weiss Kreuz fanfic I just endured:

The scene involved five people - the heroes and a Mary Sue - which is getting toward the upper limit even for a conversation. The Sue was supposed to be holding Ken at gunpoint, but there were three other people there, all of whom are trained killers, two of whom own ranged weapons. She's toast, right? Well, no. She stands there bickering with Ken for a while while the others do nothing to stop her, then another OC pitches up cackling, holding a spear. There are now six characters present of whom four are doing nothing: the Sue switches her focus to arguing with the new OC while Weiss just watch. She spends a paragraph angsting, then struggles with the newcomer who tries to disarm her. Ken finally remembers he can talk, then the new OC stabs the Sue and runs off. It's only then that Weiss realize that they can actually do stuff, and at that point the scene ends.

If you the author can't see what the problem with this is, you probably need to rethink the way you write confrontations.

Even stupider are those scenes when the bad guys hang around in the background, waiting for the heroes to stop arguing about their personal lives and come and kill them already. Once again, I've read fics where this happens: the one that sticks in my mind is a Sailor Moon fanfic where the Monster of the Day, who had just effortlessly owned the entire Inner Senshi, just stood around and waited to be killed while the overpowered Sailor Sue recited a little speech about how awesome she was then bickered with Tuxedo Mask. Sailor Sue then commented that it was a 'pretty stupid monster' because it was just standing there waiting for her to be done preening.

The question is why. Why can't a character, if they see an opening, take advantage of this? Because otherwise the scene wouldn't work?

I'm going to put it bluntly: If your plot, fangirl author, is reliant on half the characters suddenly acting like they've forgotten they can actually do things for no good reason, your plot sucks.

If the only reason that the rest of the characters in a scene are rendered largely redundant is that 'it would be cooler this way' or 'well otherwise this cool thing can't happen' - well, that's really not a good enough excuse. If an author wishes to have multiple characters present in a scene but only focus on the exploits of a pair of them, they need to provide a reason why the others aren't getting involved. This doesn't have to be a long reason, or a particularly involved one. A couple of sentences to explain why they're not getting involved would do it. Even if all you do while Ravyn McSue bonds with her would-be love interest is mention that the two other characters who were there when Ravyn showed up are now talking amongst themselves, it's still better than ignoring them.

Which brings me to the other reason: if an author is ignoring the other characters out of laziness because they don't think they're important enough to acknowledge right now, why drag them into all this in the first place? Surely it would be even easier to just not get them involved?

Now, this isn't to say that characters have to become involved all the time or the fanfic will suck. Of course some characters won't speak up or intervene in all situations: it's not normally in their nature to do so, so why should they start now? Of course, by the same token, some characters are going to be quieter than others and of course some of them will inevitably have less to contribute and will choose not to get involved for purely practical reasons. They don't all have to be jumping up and down and screaming look at me at once as if to justify their presence in the story, but no matter how quiet or withdrawn they may be by nature, or how little they can constructively contribute to the scene, they should nonetheless have a small but distinct say in how the scene proceeds.

If the only way an author can come up with for a certain plot point to be workable is for several characters to - to put it charitably - become uncharacteristically crippled by indecision or complete inertia to the extent they might as well not even be there, they really need to think a little harder if the plot point is actually workable at all. It can't be that hard to come up with a way for an OC to be stabbed which doesn't involve four out of the six characters in the room at the time standing around like lemons and letting it happen.

Besides, how interesting can a confrontation truly look if even half the cast are so utterly unconcerned that they're just standing there? Exactly.