When Springsteen station flashes into Penn Station, an Observer is standing next to the sign on the left.
The glyphs for this episode spell out: CROSS
First episode to have opening credits in both blue and red.
The brief glimpse of the exterior of Penn Station shows that, in the alternative universe, it has been renamed for New Jersey-born singer Bruce Springsteen.
There are several references to the "Lost" numbers. At the beginning of the episode Peter looks at the clock twice. The first time it reads 12:23, the second time it reads 2:15. In Penn station the shapeshifter states he has had 8 identities in the last five years. At the end the clock behind Walters head reads 4:00. 4, 8, 15 and 23 are all numbers in the Lost sequence.