Speaking of subverting expectations, a great example of good subversion of expectations is Aranea Serket becoming the main antagonist for an entire arc.
Nobody expected that. We were in the middle of a confrontation with the Condesce when suddenly a new player comes into the mix seemingly out of nowhere and messes up the entire board.
But it wasn’t out of nowhere. The motivation, means, and timing for the twist were all laid out beforehand, so when Aranea took that ring and entered the Alpha session, it made sense.
It subverted our expectations because we weren’t paying attention, because we were engrossed with the main plot. Not because it was something we couldn’t possibly know or expect since the writers made it up on the spot.
It was a great twist because up to that point she had presented herself as nothing more than a dork who was desperate to be seen as helpful, but there were also neon flashing signs saying “You should expect this character to have a similar personality to Vriska”. The twist was the reveal that her need to be helpful was really the same character motivation as Vriska’s need to be important, and she turned out to be the same but worse. And afterwards you could only realize that of course she’s the same kind of person as Vriska, you should have seen it coming but didn’t.