Well, we actually knew about Lars of the Stars since July or so, since the first couple minutes was shown back in San Diego Comic Con. As for Emerald, I've heard that it's been stated time and time again by the creators that SU has no one-off characters. Every character will be seen again at some point or another. I definitely agree that it was a nice touch not having him be totally changed, it made his character arc feel more realistic, since you don't change overnight, old habits will still break through. I imagine remembering how much he missed Sadie probably made his emotions more volatile.
I really enjoyed those too, they were really solid episodes. Oh, I was also a little surprised that this time they had Lars actually say that he died. They'd danced around it when it initially happened, with him saying 'not alive' instead of 'dead'.
Lol I don't watch previews ever, I'd rather enjoy the show when it actually airs, so I didn't know about any of those. If you imagine it from my point of view, it would be pretty surprising. And that's good to hear, with regards to the no one-off characters ---