YY Plump - and this is why it's hard to spot because lots of people have traits which narcs have but not from the same root, if that makes sense.
Oddly I was writing the list while thinking "I so do this". I'm pretty open even to strangers and don't really have the horror of "someone finding out!" my worst experiences because I don't feel ashamed of them.
I also love song lyrics but my entire facebook/twitter feed isn't comprised solely of them, which my ex's is, when he's not deleting his account in a huff or creating multiple different ones. I also didn't realise at first but after three years with him I noticed that he never had an original thought or comment, he literally always recycled something he'd heard somebody else say and quite often he didn't understand what he was saying, so he'd say it in the wrong context. For example watching X factor he'd pick a singer he didn't like and say "Oh, she's totally flat." He assumed it meant not talented, not realising it's a musical term meaning she's singing too low.
Also similar to what Fog says - we tend to, as humans and in British culture generally, assume responsibility for small accidents and feel embarrassed about them even when they aren't our fault. We don't do this consciously. So if you're out together and a drink gets spilled, or some other thing where it's not really immediately clear what has happened and it's not a big deal but it's annoying, most people's immediate reaction is to jump up and say "Oh shit, sorry!!!" and try to mop it up or prevent it from spilling even further. Internally you're thinking "Aaaargh why did I just do that, that was so stupid, why didn't I realise?"
When the other person is also a normal/emotionally healthy/nice person, they are also thinking the same thing and so in most cases it ends up as a "No no, I'm sorry! It was my fault!" or when it's obvious whose fault it was the other person is mortified that you might be upset so they go out of their way to reassure you and say "Please don't worry! It's just an accident, it really doesn't matter!" and feel stupid for leaving their paper in the way of the drink getting spilled or whatever even if they're secretly pissed off about something getting wet or ruined.
The narc and/or arsehole won't have this reaction. They will assume whatever it is can't have been their fault, therefore it must be yours, or the waitress or the table or anything - they will look for someone to blame. Usually, it's you. Unless they're a very obvious arsehole they probably won't go all out angry at you, but they will subtly let you know they are not pleased about it. Because this ties into your internal monologue of "OMG, I'm so clumsy, that was totally my fault and he's going to be pissed off because his clothes are wet", you accept their reaction as justified and don't notice anything off about it. Because the underlying feelings of this kind of incident are unconscious and over so quickly, you're not likely to analyse how you would react in the actual situation, you assume their reaction is justified because instead you imagine how you would react/feel if someone very obviously tipped a drink on you on purpose.
This is really magnified if you have low self esteem but it happens even for people with normal self esteem. You assume you're in the wrong and hence others are in the right and expect them to react as such.
Over time in the relationship this kind of reaction happens for everything, there will be little snide comments in between about your "clumsiness" or "laziness" or whatever (which again match up with your internal idea of yourself so you don't question them) and gets stronger and stronger until they are full on physically threatening and screaming over a minor incident.