Dean's relief that surely Cas can't be working with Crowley because if Cas can show up and save them from demons one second and make dumb Captain Obvious remarks the next, then surely everything is okay.

Damn you, Lass, you have me crying all over again!!!

I can't even entertain the possibility that this wonderful character may die in the finale and his famous one-liners will be lost forever... and by Dean's hand no less! *breaks into a million pieces*