tl;dr: Name your NPCs to avoid slips and obfuscate who is important.
A theme of this year has been a lot more one shots and published material - me reading and assimilating other peoples stuff with not so much prep time before running it - Light of Xaryxis campaign and the Fistful of Quatrins series in the Bracalonia book among others. What I have found this has lead to is problems for me where NPCs have false identities or hidden aspects.
This person they found has a core aspect of their identity that is not obvious on first glance.
That sailor is a shapeshifter? How to avoid slipping and referring to him by 'cultist' or 'shapeshifter'.
That voice behind the door is a monster? Better not refer to it as what it is.
That guy has a connection to people that is his only characterisation but you do not want that to spring out at folk
Solution - name them and never give another reference, even after things become clear.
Best part of this is that even after things come to blows and there are pieces on the battlefield, you just have different looking pieces but the names still obfuscate exactly what it is.
Spoilers ahead for light of Xaryxis (LoX).
My favourite example of this is the Nautiloid wreck encounter from Light of Xaryxis - you get greeted by a shapeshifted thing on approach and they try to lead you into ambush by their buddies. Left unnamed they are 'the psurlons' a slip I made the first time I ran through this (as standalone in Spelljammer Academy). The second time I ran it I named them all so it was Alfonso, Benedict, Charles etc. which worked well even after they dropped their disguises and assumed their true forms as it still was unclear, beyond the gruesome tokens, what the players were dealing with. Shock and surprise was maintained well into the encounter as opposed to 'oh, one of those' and it becomes a bag of hitpoints to chew through.
Later on there was a voice through the door - Jasper - who eventually was released to reveal a monster and despite deploying all his tricks and horrors it was never clear what the hell 'Jasper' was - leading to Jasper being pretty well remembered as a scary horror encounter.
So - for all these reasons, name your opposition to keep a realistic fog-of-war about things. To support that, name your random background folk too otherwise the few named folk stick out as if they had a glowing arrow over their heads. I realise naming NPCs can be an annoyance but this is just another reason to build out your name generator or pre-gen random lists of names. I like Fantasy Name Generator - it does what it says on the tin.
Getting this written down was prompted by Gorgon Bones 'On Hobby Best Practices - Record your hobby experience.'