I was originally thinking that many of the other characters could just be David's alters, but since they went with paranoid schizophrenia instead of DID and next week's episode trailer had Mrs Bird saying his mental illness wasn't real and just a result of his powers, I don't know if they're going to go into multiple personalities at all. That seems like a weird choice. I still wasn't convinced that at least some of them weren't alters, but the wikipedia write-up has info on several of the characters making it likely they are all real people.
That being said, the Sydney/Cyndi thing is another odd choice. Why give a character a name so close to one of Legion's most dominate personalities if there isn't supposed to be a connection? The rescue scene with the obvious pyrokinetic display seems to also link the comic and show characters a bit, but, again, I don't know if that was intended.
Also, why name your character after the bassist from Pink Floyd? Could that be a hint that at least Sydney isn't real, that David might have just been a Floyd fan and named one of his alters after him? But again, the chick, Lenny I think her name was, that ended up in the wall (fucking hell) also saw Sydney. Now I'm wondering if everyone in that group therapy session could have been an alter. Shit. Fucking unreliable narrator.
The little yellow-eyed goblin seems similar to another Legion alter, the Fiend. That is before the Fiend morphs into a Charles Xavier-looking guy. The Fiend had precog abilities, so I was trying to see if his appearance could have been during moments where David was actually getting a glimpse of the future.
Anyway, I don't really know how I feel about this yet. It's pretty surreal, which is fine, but I don't want oddity for its own sake. I'll give it a couple more.