Walter remembers Astrid's name for the first time, but when he turns to her he finds the Observer there instead. No one else witnesses it.
According to her driver's license, Nancy Lewis was born on 3-26. This number appears many times throughout the series and happens to be the birth date of Leonard Nimoy.
The glyphs in this episode spell "Vision".
Stephen King did actually coin the term "Pyrokinesis" when writing "Firestarter" in 1980.
Grayson has a Vulcan harp in his apartment.