This episode follows the pattern established in season two: The fourth-to-last episode of a season is "the weird one". Season two (23 eps) had #2.20, Brown Betty, a musical, whereas season three (22 eps) had #3.19, Lysergic Acid Diethylamide, a partly animated episode. And this one is a flash-forward episode.
The glyphs for this episode spell out: QUAKE
This is one of only two episodes in which Anna Torv (Olivia Dunham) did not appear. The other being Subject 13 (S03E15).
Henry Ian Cusick, who plays Simon Foster in this episode, also played the central character Desmond Hume in Lost (2004). Lost was another JJ Abrams production.
The glyph on the face of the loyalist who stops Henrietta, Simon and Walter at the transit station reads 1776. No doubt a nod to another "fight for freedom"