In many cultures, a white tulip represents forgiveness. In can also represent heaven on earth/perfection, making it an apt symbol for Walter.
Guest star Peter Weller plays a scientist who has implanted mechanical and electrical devices in his body that give him special abilities - the dictionary definition of a "cyborg." Weller is most famous for playing the lead role in the RoboCop movies, in which his character is a cyborg police officer.
The Observer stands in a doorway near the accident that kills the time-travelling astrophysicist and his fiancee.
The glyphs in this episode spell out: SECRET
Twenty minutes in, a small sea horse can be seen in the bathroom cabinet of the former NASA employee. Sea horses appear all through the series. As revealed in "The Bishop Revival" (S02 E14), the sea horse was a signature used by Dr. Walter Bishop's father in his scientific experiments.