Is it ok to put a subplot to a story that is never meant to contribute to the development of the main plot? In Game of Thrones season 8, a lot of the subplots that were explored in previous seasons were completely dismissed or ignored. While this is an example that tells you it's a bad thing, is there a good case for doing this? When is it ok to do this and why? Could you provide some examples?
Everything in your story should have a purpose. That purpose does not need to be plot related
Possible purposes for a side plot in a story:
It is connected to the main plot
It causes character development
It shows existing character traits to the reader
It echoes the themes of the story
It enhances the symbolism of the story
It develops the setting
Ideally, your subplot will be doing several of these things at once. The more distantly related a subplot is from the main story, the shorter it should be, because readers will be less invested in your side story and want to get back to the main story. (Or worse, they become more invested in the side story, and start wishing that you would ditch the main story, which you absolutely don't want).
If you want to read an example of sideplots done excellently, I recommend The Lies of Locke Lamora, by Scott Lynch. The story is peppered with flashbacks and expository stories which have little to no bearing on the main plot, but provide excellent context that helps frame character, setting, and theme. (One story in particular is about a sporting event that took place several decades prior, involving no relevant characters and a sport which is never mentioned again in the book. Its purpose was to be an object lesson in how the people of this city regarded revenge, and that's it.)
As I am prone to do perhaps too often in this forum, I say it depends. Mostly upon what your intentions are. That is, why did you write the story in the first place.
Let me take an "extreme" position and then back off from it.
Everything in the story must advance the theme or central question that the story presents. If there is a side story, that part of the story must present a complementary view of your theme. Let's say that your them is that of courage. Every thread in the story must concern courage. Some might address the hero that appears courageous but never really understood the risks that the heroic action entailed. Another might address the hero who did understand the risks and acted anyway; there might be multiple stories in which the motivation was honor, ambition, friendship/loyalty, and so on. Still another might address the consequences of lacking courage. The point is that the reader comes away from the story with a clear impression, "The story was about courage."
Absolutely no exceptions.
Well, maybe a few.
The purpose of the author is to manage the reader's experience. If the story is dark, a prolonged experience of a 100 pages of darkness might well turn the reader off. Interjecting the darkness with flashes of light (that are not thematically related) may be necessary to preserve the sanity of the reader. Gallows humor, if you will. It happens in real life. It happens in stories.
This business of writing really only has suggestions and guidelines. No rules. If you stray from the proven, AND THE READER BUYS INTO WHAT YOU DID, YOU WIN.
And so I cycle back to the notion of what your intentions are when you do something "odd." The only real question is whether you accomplished your intention.
P.S., although I have not watched Season 8 of GoT, I am aware of the dissatisfaction expressed by fans. But I will note that the finale was watched by a record number of viewers. Hard to call that a failure.
I dimly recall Nabokov, not in a work of fiction but in writing about writing, mentioned approvingly that some author (Chekov?) would often do this, just a few off-the-cuff comments from a character invoking an entire group of people in the reader's or drama audience's mind we never hear about again. To capture the flavor as best I remember 30 years after reading it: "oh, my uncle had the same problem with my cousins, they had to fire their Belgian nanny and get a..." whereupon they're interrupted by the actual play progressing. You have this miniature avalanche of characters out of nowhere, who nonetheless are almost memorable despite not hearing any more about them.
More generally in Nabokov there are lots of "easter eggs" hidden around that have nothing to do with the plot. At one point the contents of a toy box are described, and include a chess set with a pen cap standing in for a lost piece. Half a novel later a secret drawer is opened in an old desk, and found to contain a few items including a worn black rook. Probably the missing piece. It's not quite a subplot, but it is a beautiful little detail that certainly doesn't drive the main plot forward.
TLDR : Your subplot doesn't have to contribute to the main plot, but it does have to connect
Long version with Harry Potter examples :
In my experience, there are three ways to 'connect' a subplot to the main plot :
- Directly : Let's say your main plot is Alisha, Bob, and Cara teaming up to destroy the evil Dan. The subplot of how Alisha and Cara have to leave Bob behind to get the fabled weapon, Dan-killer, from a women-only city, is a subplot that directly contributes to the main one, because they use Dan-killer to, well, kill Dan.
In the Goblet of Fire, we learn at the beginning that a Ministry employee, Bertha Jorkins, has gone missing. Whatever, we only care about Harry and his school shenanigans. Later, we learn that Voldemort killed her after learning about Barty Crouch Jr.'s escape from her. This is why he orders Crouch to get Harry to him, and it leads to Crouch putting Harry's name in the Goblet, which starts the main plot (Harry being a champion in the Triwizard Tournament)
- Through a Character : While Alisha and Cara are off getting Dan-killer, Bob helps a little kid learn how to harness their magic and not be afraid of it. The audience gets to see how kind and sweet Bob is, maybe learn that he has a younger sibling. During their victory parade, the little kid waves to Bob. Note that if the little kid ends up using their magic to help kill Dan or get into his castle in some way, this becomes an example for #1. These subplots often revolve around side characters.
We don't need to know that James Potter was an ass. If Snape hated him just because he dated Lily, and Lily and James got together without ever hating each other, it wouldn't impact the main Harry-defeating-Voldemort plot. Knowing how James behaved is kind of like a bonus for us, extra information about a character that we've heard about. It also gives us an insight into Harry's character - he thinks behaviour like that is jerkish and he hero-worships his parents (he's horrified when he learns his dad behaved like that). Everything about James could've been cut from the books without too much trouble - we just wouldn't have gotten as much detail.
- Thematically : Alisha and Bob have always been overprotective of Cara, the youngest one. When Cara is held hostage by Dan, Alisha and Bob have to choose between trusting her to be able to make it out okay or handing over Dan-killer. They don't trust her, leading to the death of civilians and side characters while they try to retrieve Dan-killer, and Cara being extremely angry at them.
- Simultaneously, Eli, a peasant who is in a wheelchair, needs medicine for his desperately sick wife. He can either go get it himself, using the common roads which are accessible for him, or send his daughter Fiona, who can cut through a dangerous mountain range and come back quicker. Fiona insists she can do it. Eli chooses to trust her. The mother is saved in the brink of time - Eli realizes that if he'd gone, she would've died.
- This one is longer and my example is heavy handed, but it's basically about parallel themes, which can either go the same way or in completely opposite directions. These tend to coincide with #2, in the sense that the audience would've already been introduced to either Eli or Fiona or the mother.
In Prisoner of Azkaban, Buckbeak's story parallels Sirius Black's. Both are allegedly dangerous, framed for a crime they didn't commit, and Harry helps them both escape. In this case, however, Buckbeak's sub-plot does also tie in with the main plot.
Another thing that could be done is having multiple plots simultaneously, like the first season of Game of Thrones. However, all of the plots in GoT would be considered main ones, and even when they were disjoint, the promise of them coming together always existed.
EDIT : forgot another type - the side plots that are just to exposit on the setting of the story
@Arcanist Lupus says it much more concisely than I do!
I'd like to add an economic point of view.
The reader is an investor, his currency is both emotion and time and his payoff is the satisfaction from consuming your story.
(I intentionally skip the monetary expenditure to purchase the work as it may not apply to all of them).
This means that every chapter should contribute to the total value of the work, in terms of the emotional and satisfaction payoff the reader got from investing in that chapter. A side story about their favorite character will be like a short-term investiment with low risk. When the side story ends, the payoff is there already. One that contributes to the major plotline will only pay off when that line comes to dividends.
As long as the reader can see the good in investing his time, he'll happily go for the subplot that broadens his (already made) investment.
I can think of two things you should not do:
Introduce a new character with a side story that has little to no hooks with the main story. I usually skip those and come back after the new character became relevant. It is like buying stock in a startup you know nothing of. It can pay a thousand times in a year or it can be a flop. I have a lot to read and am my aversion to risk is high.
Build up an investment and suddenly dump it without the payoff. For an example, a web fantasy author wrote around 100k words regarding a group of side characters (the whole thing is nearing 4M words now) and their plight. We got hooked to it and eager to see how each of these characters would turn out. Some of them were tertiary toons from the early times of the work. It skipped #1 entirely because they were already woven into the story. And then they are thrown into a conundrum, and their outlook becomes dire. They were herded into war by an enemy to fight a third party in order to weaken both so that enemy could reap the victory against all. They revolt in the end and stop the enemy from overrunning the thrid party, only to be overrun by that same third party. The enemy was left out without their victory but without much losses, while these characters you invested so much in were slaughtered and then forgotten. The story has two chapters with only the MC grieving and then live goes on. I'd rather hold Lehman Brothers stock.
Bottom Line: It is fine as long you can show your reader the value of investing time in reading your subplot and give him a satisfying payoff.