At the end of the episode, Jack, Kate, Sawyer, Hurley, Claire (and possibly Rose, Bernard, Vincent, Cindy, Zack, Emma and others who defected to "The Others") are the only remaining survivors from flight 815.
The warning klaxon in the submarine is the same sound from the Swan.
When discussing Locke's father's condition, Jack tells Locke, "Whatever happened, happened." This is also the name of a fifth season episode.
In the flash-sideways, Jack tells Locke that his surgery was difficult because his dural sac had ruptured. In the first episode of the series, Jack tells Kate about an incident early in his career when a patient's dural sac ruptures (as the result of his mistake) and about how he forced himself to deal with the consequences and remain calm.
When Jack gets the C-4 out of the backpack, the countdown goes from 3:55 to 3:52. It then beeps 10 times (one beep per second), leading the countdown to 3:42. However, the scene after, the countdown is at 3:45.
Jack buys an Apollo Bar from the vending machine at the hospital.
Hurley says he cannot find the First Aid Kit. The Kit can be seen in the control room next to Frank.
There are 4 bricks of C-4.
The Apollo Bar is located at E3 in the vending machine. E is the 5th letter in the alphabet. 5+3=8. Also, 5x3=15.
Four people escaped from the sinking submarine.
Locke: You sure you won't reconsider, Jack?
Jack: Yeah, I'm sure.
Locke: Whoever told you you needed to stay had no idea what they were talking about.
Jack: John Locke told me I needed to stay.
Fred Koehler (Seamus) appears as a guest star, where in all other appearances he was credited as a co-star.
According to Jorge Garcia's "Geronimo Jack's Beard" podcast, in the script, Locke also said "It's a two men job" in his sleep.
This episode breaks the record of most main character deaths with 3 (Sayid, Jin and Sun). This record was previously held by "Exposé" with 2 (Nikki and Paulo).
There is no "Previously on Lost" in this episode.
As of this episode, there have been 14 episodes this season and Desmond only appeared in 5 of them. This breaks the record of Michael in Season 4 and Nikki in Season 3 who only appeared in 6 episodes out of their 14 credited episodes.
A Jack/Locke-centric episode.
Though credited, Nestor Carbonell (Richard), Henry Ian Cusick (Desmond), Michael Emerson (Ben), Ken Leung (Miles) and Zuleikha Robinson (Ilana) do not appear in this episode.
Original International Air Dates:
Canada: May 4, 2010 on CTV
Australia: May 5, 2010 on 7TWO
United Kingdom: May 7, 2010 on Sky1/Sky1 HD
Portugal: May 11, 2010 on FOX/FOX HD
Spain: May 11, 2010 on FOX
Finland: May 20, 2010 on Nelonen
Norway: June 2, 2010 on TVNorge
Germany: June 16, 2010 on FOX
Sweden: June 30, 2010 on TV4
Czech Republic: July 5, 2010 on AXN
Pillsbury Doughboy: Sawyer calls Seamus "doughboy", after this advertising icon and mascot of The Pillsbury Company.
Eric 'Hoss' Cartwright: Sawyer calls the submarine captain "Hoss", a nickname he has used before to label characters who he needs to do something for him.