Spoilers ahead for "Beyond the Wall" (Game of Thrones, S07E06)
Toward the end of the episode, "Beyond the Wall" (Game of Thrones, S07E06), we see a close-up shot of Longclaw
Then, once Jon Snow emerges from the water, Longclaw appears to be opening its eyes
You can get a much better picture of it in this imgur album, which shows the event happening, frame by frame, with comments.
Is this an Easter Egg from the Visual Effects department, or is there an in-universe explanation behind this?
Or was this not planned at all by the production team, and this is merely a coincidental, accidental lighting/water effect, that just happens to be timed with the dramatic tension of Jon Snow possibly being dead, and the relief of him being alive?