I really did love The End (5.04) and Croatoan (2.09). I remember after Croatoan aired fandom complained (quite a bit!) about it not making sense. That this virus was introduced without any follow up (what did it mean that sam was immune? etc). And there it was, 3 seasons later with a full explanation. Looking back, it's great to see how many of the episodes tied into the 5 year story arc. It also remains my favourite Jensen episode of all time. His acting was top shelf. And even though Sam didn't appear much, he had a huge impact when he did.
I made this vid. I remember wanting to look at the reasons why Sam ended up becoming Lucifer's vessel (also, The Doors' "This is the End" song wouldn't leave me alone!). I also wanted to twist it a little by suggesting that actually this is how it ended. :(
I think this episode serves as a reminder of what happens if they they fail to "keep each other human". It's still a very strong theme, even now. In fact, I'd say more now than ever.
It's been lovely to see all the Croatoan celebration posts around. Fandom can be pretty damn positive when it wants to be. :)