When Aaron is first taken to Walter's lab at Harvard, an Observer can be seen walking by in the lower left hand corner.
The glyphs for this episode spell out: REBORN
Walter explains to Olivia the spores on the bodies are cordyceps fungi. Cordyceps fungi are what cause people to mutate in the Playstation game The Last of Us. This episode premiered 2 years before the game was released. Anna Torv plays the live action version of Tess, a character in the game, in the HBO adaptation that premiered in 2023.