The title of this episode is a Japanese word, written as 二世, that refers to those of Japanese ancestry born outside of Japan to a first generation, or Issei (一世), immigrant. More information on Nisei can be found here.

When Mulder asks Skinner at the Allentown Police Station if he speaks Japanese, maybe he should have been asking the Fox censors if they spoke Japanese. A few scenes before, when Mulder cocks his gun at the Japanese diplomat, the man says Kuso. Written as 糞, the word means excrement, but the meaning changes with the pitch of the voice. In this case, since the second syllable is drawn out, the man is actually saying shit.

The photos that Mulder shows Scully of the atrocities that were performed on humans bears the red stamp 極秘 (Gokuhi). In English, it says Top Secret.

Langly: The name of the boat is the Talapus. Just gotta love them German optics.
Mulder: So you're saying that's from a German satellite?
Byers: No, the optics are German. The technology is probably ours, but the satellite is most likely Japanese.
Frohike: Launched from South America.
Mulder: Gotta love that global economy, huh?

When Senator Matheson informs Mulder of the assassination fo the four Japanese, he states that the murders had happened several weeks earlier. When Mulder briefs Scully, he says someone must have been able to identify the four doctors, because they were slain the day before.

The exterior shot of the Allentown police station is of a building surrounded by several trees and captioned as Substation C. However, the Allentown police station is actually in the heart of the city, and is not sectioned alphabetically.