I used to lament that this whole portrayal of friendship was horrendously unrealistic, and that not everyone only has one friend and never talks to anyone else in their class, surely. But then I read Louise Rennison's Confessions of Georgia Nicolson series, and I understood why. Georgia Nicolson has so many friends that I have only ever managed to get my head around two of them. (A little research reveals that Georgia Nicholson only actually has five friends. Which just goes to show how few fictional characters I can cope with.)
The problem here is not actually with the number of characters in the work, but the number of characters who serve the same purpose. All of them just blur into one 'friend'. I'm sure they have distinguishing traits, but they don't really have distinguishing effects on the plot. I've been facing a similar problem while editing recently: not so much that I worry that readers will forget who my characters are, but that they will be bored by all the minor walk-on-walk-off characters, and although they might remember who they are, they won't actually care.
The answer to readers' lack of interest in who your myriad of characters are is, I believe, to merge them. And on that note, I offer some thoughts which will hopefully help you know when to start merging, and when to stop (before your work ends up with just one incredibly conflicted character).
- Label your characters with those horribly stifling labels such as 'protagonist' and 'comic relief'. Look at characters who share a label, and work out if they provide some sort of contrast or conflict to each other. If you have two protagonists who never argue, both strive for the same goal and have similar personalities - well, why do you have two protagonists?
- Find characters who serve the same purpose in terms of their actions within the story. If Alice and Bob are both there to provide support to the protagonist, although one does it in the role of love interest, and the other of comic relief, why not make the love interest more comic, and do away with Bob altogether?
- Do two of your characters always appear as a pair? And when I say 'always appear as a pair' I mean that they are literally never on screen (or page) alone, and that they may as well be conjoined twins.If there's no reason why you have two of them rather than one, it may be better to just have one.
- I often find myself with characters who are around for long enough that I start to feel awkward calling them 'the man in the hat', but not around for so long that I feel like I should give them a name and a backstory. If you have any characters that have reached this awkward stage, look out for characters who already have names and backstory, who aren't doing much at the moment and could fill their role instead.
- At the end of the day, some characters are just really boring. In the first draft that I am currently editing, I had a major character - possibly the third-main character - who I just found really, really dull. She was instrumental in driving the early plot, and she took an active role in it, but she was also incredibly boring. So I took her role, and gave it to a very minor character who I really liked for no good reason. I now I have a major character who I like with good reason. Everybody wins!