Apparently a lot of people didn't notice, but I had __tiana__ going crazy on Gtalk all last night repeatedly coming back to that very scene.
I take it as Dean's fears manifesting itself in something that he isn't sure whether he saw it or not. Sam had asked him about what he saw near the end, and Dean didn't want to tell him, but Sam going YED is his biggest and probably one of the only true fears that he has.
I was flipping out when I saw that last night. And my SFC recap ends with me pretty much flipping out over it. It was an unsettling episode to begin with, and that just tipped the scales. I'm so worried for Sam now!
looking at people's episode reactions, I seem to be one of the minority who noticed it on first viewing. It was so clear to me. Clearly a matter of looking in the right place at the right time. Now I want to know if it was Dean or Sam. (ie another hallucination/imagination, or real)
I sure as hell noticed! I almost spilled the cat off my lap, yelping out loud at it! It was just sort of a passing wash of yellow, like a cloud across the sun, but GAH!
I do, however, think it was still like ... a hallucination hangover for Dean, a last glimpse of a very real fear. As well as Kripke dropping an anvil on us in warning. *G* Sam may not really go YED on us, but I'll bet anything there is Something Horribly Scary in the pipeline for our Sam. *worries*
A final worriesome moment in a very troubling episode. Thanks for the perfect screen cap, lady! I'm gonna save it, if you don't mind. :-)
I just assumed it was meant to represent Dean remembering his hallucination of Evil!Sam and the seed of doubt in Sam it planted in Dean, not that Sam's eyes actually turned yellow.