This episode's glyphs spell:
Each Olivia successfully crossed back into their home worlds in this episode.
The Observer can be seen standing outside of Penn Station before the Fringe team catches up with Fauxlivia.
A sign outside of Astoria Holy Witness Church in 'The Abducted' says "He That Enters Here Shall Be SAVED!". The bond formed between Olivia and Alt Broyles while working this case is ultimately what saves Olivia from death and allows her to return to her universe in 'Entrada'.
The electronic billboard outside Springsteen Station in 'Entrada' displays advertising for "Mercy Ballet", foreshadowing the victim of 'Marionette' being strung up like a puppet and made to dance like a ballerina.
The teleportation destination for David Robert Jones in "Safe" was anchored by harmonic rods, which are often used as tools used in crossing over as seen in "Entrada" when harmonic rods implanted in Fauxlivia help bring her back to her universe. (Image 1)
Both versions of Broyles hold their respective Olivias in similarly high regard.
Broyles saw dead Alt Broyles in "Entrada" and it had been haunting him.