The premise of this episode reminded me a little of Something Wicked from S1, especially with the kids getting attacked and then being in comas. It wasn't exactly like that & went beyond that, of course, but it just kind of reminded me of that somewhat.
It was cool to see Bobby and Rufus again, as cantankerous as they were with each other, and it seemed that they meshed the flashback scenes with the present-day scenes quite well. I noticed they set up some parallels between Bobby and Dean. Bobby was sleeping in his car because he was consumed with finding ways to stop the apocalypse, while Dean was at least somewhat consumed with finding ways to stop Amara. I do have a pretty big quibble over continuity, though. With the mention of the apocalypse, it seems the flashbacks would have taken place during season 5. But Bobby should be in a wheelchair then, unless they took place either after 5x21 or before 5x01. The latter would seem to make sense, but then in the phone call at the end Dean tells Bobby they had a lead on Lilith. She was killed at the end of 4x22, so this means it would have to take place during season 4. Maybe I'm too nitpicky and to be honest I haven't rewatched S4 in a long time....was there a lot of talk during that season about the apocalypse? Not until the end of the season at least?
Anyway, I saw that while Bobby was in that coma state, his worst nightmare was seeing both the boys dead. Aww :( And then while Dean was in that state, his worst nightmare was seeing Sam dead. Although did I miss something or did he seem to not really react much to that? I was a bit distracted while watching some of this... Also I'm not sure if I got this wrong, but was it Dean who saw Bobby as one of the "sick people" who started vanishing at the end right before he woke up and had Sam tending to him? Or was it Bobby before he was waking up see a "sick person" Dean start vanishing? They melded those scenes together so much I think it confused me a little.
All in all it was like another old school MOTW episode (the opening scene reminded me of something we might have seen during S1, at least the way it was done). Some nice brother scenes and I loved the return of Rock, Scissors & Paper (although Dean seems to have lost again! LOL). Oh and the boys driving away at the end to some rock music, even if it was very brief.