After Nagilum tells the bridge crew that it will take a third to a half of the crew to explore different methods of death, there is a shot of the supposedly dead Haskell with flaring nostrils.
Just after Data launches the first stationary beacon, Picard turns to talk to Geordi at the bridge engineering station. When Picard starts to turn and walk towards the back, Geordi can be seen standing, facing the turbo lift; but as soon as the scene cuts to Geordi, Geordi instantly pulls out the chair for the station and sits down facing the opposite direction.
When Data first tries to hail the Yamato, Riker and Picard are facing their screens with their backs to the camera. Riker is standing close to the screen while Picard is further back. When the camera cuts to a reverse shot from their front, Picard and Riker are standing practically shoulder to shoulder. When the shot reverts to the rear shot, they are once again standing apart.
Data says that there have been no similar occurrence in the distant past, but there was a similar event in the original Star Trek series episode "The Immunity Syndrome," when there was a void in space, a creature in the void, and two probes went dead.
In the Season 1 episode "11001001," the time interval for self-destruct was set to five minutes. Picard said there was no other choice. How is it, then, that this time the computer asks Picard and Riker what time interval they wanted?
Deanna is originally sitting on the bridge when they approach the zone of darkness, but after Picard tells Wesley to take them in, in the next wide shot Deanna disappears entirely and doesn't reappear throughout the rest of the scene. She only reappears much later when Riker and Worf return from the Yamato.
Not exactly a goof, but for some reason Nagilum is on a first-name basis with LaForge; he refers to everyone else by their last name but calls the Chief Engineer "Geordi."
Over this and several other eisodes of TNG, an error made by a writer resulted in the lack of continuity of O'Brien's rank; he is referred to as "Lieutenant" instead of "Chief."
(Captain Picard when asked, "What is Death?", by Data)
Picard: Some see it as a changing into an indestructible form, forever unchanging. They believe that the purpose of the entire universe is to then maintain that form in an earthlike garden which will give delight and pleasure through all eternity. On the other hand, there are those that hold on to the idea of us blinking into nothingness (Picard snaps his fingers), with all of our experiences and hopes and dreams merely a delusion.
Data: Which do you believe sir?
Picard: Considering the marvelous complexity of our universe, its clockwork perfection, its balances of this against that... matter, energy, gravitation, time, dimension, I believe that our existence must be more then either of these philosophies, that what we are goes beyond Euclidean or other "practical" measuring systems, and that our existence is part of a reality beyond what we understand now as reality.
Nagilum: Masculine and feminine. I understand.
Picard: Yes. That is how we propagate our species.
Nagilum: Please demonstrate.
Pulaski: Not likely!
(when asked to concur about stopping the self-destruct)
Riker: Yes, absolutely, I do indeed concur, wholeheartedly!
(Refering to Nagilum's projected face)
Data: Captain, sensors show nothing out there. Absolutely nothing.
Geordi: Sure is a damn ugly nothing.
Data: I have a question, sir.
Picard: Yes, Data, what is it?
Data: What is death?
Picard: Oh, is that all?
Music: "Gymnopédie No. 1." (Erik Satie)
Earl Boen (Nagilum) also supplied the voice of the Vohrsoth, the principle villain, in the 2000 PC CD-ROM game Star Trek: Voyager--Elite Force.
First mention of any sister ship of Galaxy class starships. The Yamato is "seen" in this episode when Nagilum prepares a nearly perfect copy of the ship in order to test the crew's reactions.
"Nagilum" is Muligan spelled backwards. Originally actor Richard Mulligan was to play the alien creature, but had to back out at the last minute.
This is a reference to the 70s anime series Space Battleship Yamato, more popularly known as Star Blazers outside of Japan. In the anime series, the Yamato, the pride of the Japanese Navy, is destroyed in World War II, then resurrected and turned into a "space battleship" to journey to a far away system in a quest to save humanity. There would ultimately be five story arcs/seasons, and the Yamato would be destroyed and rebuilt and destroyed again. Here the Yamato is the sister ship of the Enterprise.