The glyphs for this episode spell out: UNITES
In this episode, Walter describes he got his glasses from his friend "Dr Jacoby...from Washington State." This is a sly reference to the TV show Twin Peaks (1990). The character Dr. Jacoby wore a similar pair of glasses and the setting for the show can be assumed to be set within Washington State.
Several strong references to the Back to the Future (1985), most notably the presence of Christopher Lloyd (Doc). He receives a visit from his son, as a result of time travel. This son died in 1985, the year the film was released.
The song playing when Walter brings Peter soup at the end of the episode is a version of "If I Only Had a Brain," from The Wizard of Oz.
The Observer has an earring hole in his left ear, as can be seen when he's talking to Walter in the park.