I digress. What I really meant to say here was that jesus, Sam was epically chilled out during this whole ep. XD Like...
Dean: omg Ellen's going to be mad at me :S
Sam: w/e man, coffee 8D
Dean: omg Jo disappeared into the walls :O
Sam: cool story, bro 8D
Dean: omg Jo D;
Sam: uh huh, yeah you said that already 8D
Sure, maybe this was for plot reasons, because the episode is about Jo and Bill and Dean and John and grief-driven familial legacies, and Sam's still kind of like, yeah, I'm so not here for that, wake me up when September ends, etc.
But as of S10, eight and a half goddamn years later, we know the true reason for Sam's chill. It's really all just a forced veneer of stoicism because inside Sam's just like YAY OMG H.H. HOLMES MY FAVE MULTIPLE MURDERER THIS IS THE BEST DAY EVER SERIAL KILLERS YAY. NOW I CAN DIE HAPPY. / WAIT, FUCK. SCRATCH THAT FROM THE RECORD. TBTB, YOU DIDN'T HEAR THAT. / ...H.H. HOLMES THO. :D
I mean, jesus, look at this face: