This may already have been mentioned in the thread but didn't Joss also used to write for the comedy series, Roseanne? And didn't that end with the audience finding out the show had all been an imagined version of the main character's real family, where in reality everyone was similar but just a little bit different? Never saw it for myself but I'm certain I read that somewhere.
As for Normal Again, I always took that last scene to be Buffy finally putting her imaginary asylum self to sleep, once and for all. The real Sunnydale Buffy giving her dream self closure, if you like. She still hadn't taken the antidote when we saw the scene so it's entirely possible that it was just part of her imagined world.
On the flipside, who is to say that both aren't real? Maybe the demon's venom acts as a connection between yourself and an alternate reality version of you and Buffy was suddenly experiencing the life of an alternate Buffy.
What if, in that world, Buffy really did never leave the asylum and her mum and dad never split because of that fact. Buffy never moved to Sunnydale and, along with all sorts of other stuff, Dawn was never sent to her. That wouldn't mean that in that reality vampires, demons and hellmouths weren't really real, just that Buffy wasn't fighting them. It's not like most of the residents of Sunnydale believed monsters were real most of the time and they lived over the Hellmouth so why would alternate Buffy's doctor believe they were anything but mythological? It's definitely possible that we could have been seeing a real alternate version of Buffy in that world and that our Buffy was connected to her for a while.
At least that way both theories are right and both Buffy's are real.
