Never getting over how the writers and production team put this scene in 10x01 together!
First, Cas could have been sick anywhere. I, for one, prefer to be sick on my couch. It’s easier to watch TV, surf the net, move from laying down and napping to sitting up, etc. Anyhow.
THEY CHOSE TO MAKE HIM SICK IN BED. A bed is an intimate place, and Cas is in his bed. The unoccupied half of his bed? Covered in a PLAID bedspread (Winchester plaid, as if a certain Winchester is absent).
What’s he doing in his bed?
PINING. Cas is in his bed, pining away for Dean. They chose to have him wasting away from missing Dean – not doing the myriad of other things a sick person does in bed to whittle away at the time (like listen to music, watch tv, read, etc.)
Gah, the level of intimacy is just mind-boggling!
THEY CHOSE TO MAKE HIM SEMI-NAKED. Not only is he in bed, pining, but he’s exposed for all the world to see. His chest is bare, his stomach, his leg. We see it all.
In Supernatural, the number of layers of clothing Castiel’s wearing exposes how vulnerable he is. So as a powered up angel on a mission, he’s got a dress shirt, a suit coat, and a raincoat on. As a human, he usually just went around in a single layer. And at his weakest, most vulnerable, most tormented moments, he’s usually been half-naked (or at least had his chest, or heart, exposed).
HE SAID “I MISS HIM." And did Sam respond with "Yeah, me too” or “Me too”? No. Instead the writers had Sam just say “Yeah.” Agreeing with Cas, but not identifying with him.
In other words, Sam knows that the way Cas is missing Dean is an altogether different experience than the way that Sam is missing Dean. Sam is saying “Yeah” as in “I know you miss him. Of course you do.”
Coupled with the bed, the plaid, the pining, and the nakedness, Sam’s “yeah” response makes it clear that Cas is actually lovesick – missing a romantic love.
Imagine the same scene but with Cas curled up in a chair or couch, wearing his PJs, covered by a blanket, doing a crossword puzzle when Sam called. You know he’s sick because you see him blow his nose. He tells Sam “I miss him” and Sam says, “Me too."
THAT’S HOW YOU SHOW A FRIEND MISSING ANOTHER FRIEND.