When he first meets Jacob, Richard Alpert asks if he is The Devil. Mark Pellegrino not only plays Lucifer on Supernatural but also previously starred as a servant of the Devil in Brimstone.
Sawyer referring to Charlie as "the Munchkin" in "Tricia Tanaka is Dead" could be construed as a reference to his resemblance to a Hobbit, especially given the slight smile that starts to appear before the shot cuts.
Charlie definitely gets one in an earlier episode "Further Instructions" during which a mute John Locke is trying to convey a message and Charlie remarks, "Trees? Yeah, I've heard they're wonderful conversationalists." This is a direct allusion to the fact that Dominac Monaghan played Merry in the Lord of the Rings films and did in fact talk to the trees.
Back in the Season 1 episode "All the best Cowboys had Daddy issues", where Charlie and Claire get kidnapped and Charlie subtly leaves behind some of the bandages he wore as a trail for the pursuers to follow. It seems he learned that trick from Pippin. He was talking to Rose when she was carrying a ring on a chain around her neck.
A rare soundtrack example: Michael Giacchino, the series composer, also composed for Medal of Honor. Because of this, nearly every appearance of a submarine is accompanied by the submarine theme from the game.
One of the funniest is in "Across the Sea" when Mother asks the other woman what her name is. She responds with "Claudia". Mother smiles and says it's a lovely name. The actress who plays Mother is Allison Janney, who is probably best known for playing C.J. (Claudia Jean) on The West Wing.
In "Expose," Rodrigo Santoro's character is referred to as "The Wolfgang Puck of Brazil." This is probably a reference to Santoro's title of "The Tom Cruise of Brazil."
Terry O'Quinn, the actor who plays Locke, played an Admiral on the Star Trek: The Next Generation episode "The Pegasus". Here's a conversation from "All the Best Cowboys Have Daddy Issues":
Boone:Red shirt. Locke: Huh? Boone: Ever watch Star Trek? Locke:Nah, not really. Boone: The crew guys that would go down to the planet with the main guys, the captain and the guy with the pointy ears, they always wore red shirts. And they always got killed. Locke: Yeah? Boone: Yeah. Locke: Sounds like a piss-poor captain.
When he first meets Jacob, one of the first things Richard Alpert asks him is he is The Devil as the Man In Black told him he was in hell. This is almost certainly a reference to Mark Pellegrino's role as Lucifer in Supernatural.
Dawson Casting: Averted with Tania Raymonde, who started the show at 16, the same age as her character Alex. She experienced a touch of this though four years later playing the character at the same age. Later played straight with Alex's boyfriend Karl, played by 25-year-old Blake Bashoff.
Daniel Faraday's age is an odd subject: Assuming he was born in late 1977, that still means he was no older than 19 when Desmond visited him at Oxford where he was a professor. The fact that he's a super-genius could maybe justify that, but it still means that Daniel was probably 18 when he graduated, and in his graduation scene he is played by 39-year-old Jeremy Davies.
Ben and Danielle are also supposed to be the same age (as are Michael Emerson and Mira Furlan, who are both in their 50's). Yet when they're seen together in a flashback, Danielle at 29 is played by Melissa Farman, while Ben at 29 is played by Michael Emerson (wearing a wig).
Executive Veto: Jack was supposed to die in the first episode; ABC nixed that idea and the rest is history.
It's not so surprising that one nickname would refer to both the original castaways and the fans, given that for most of the first two seasons the fans also felt like they'd been wrecked on a mysterious island with absolutely no clue what was happening...
God Never Said That: The producers never said that the show would never have time travel. They once said that the then ongoing season two had no time travel — and it didn't — but never that there would never be time travel. Additionally, they never stated that there was one huge clue left in the pilot — in fact, they explicitly said there wasn't, and the last one to be made significant was the single white tennis shoe Jack found. Yet this is repeated until today.
In an example of "Word of Mistaken God," an excellent way to see if someone is making something up about a producer comment is to see if they attribute it to J.J. Abrams, who has had little involvement in the series since season 1, helping to set it up, write and direct the pilot, and contributing to only a very few episodes since (the last being the S3 premier).
Linwood got "lost" after getting killed off by Wolfram and Hart.
I Knew It: Speculation was that based off his nickname, "Mr. Friendly", Tom's full name was Tom Friendly. Eventually the producers confirmed this was true.
A number of fans also speculated that Tom was gay after he told Kate, "You're not my type," and the actor apparently changed his portrayal based on the fan reaction to that line. The episode "Meet Kevin Johnson" later confirmed that Tom was gay.
On a more plot-relevant level, a lot of fans, upon finding out that post-return to the Island, Locke is not really Locke anymore, speculated that he was actually the Smoke Monster in Locke's form. Sure enough, in the Season 6 premiere...
There was a planned subplot, revealed at Comic Con, that had the DHARMA researchers know that a Stable Time Loop was going on, and that they would perish. It was dropped, due to time constraints and new writers.
The original mythology was going to be much more sci-fi oriented.
Jennifer Jason Leigh was approached to play the part of Libby, but she declined.
In the original description for Kate, she was a slightly older woman separated from her husband, who went to the bathroom in the tail-section of the plane. However, that idea ended up being used for the character Rose.
Eko was originally to be named "Emeka".
The character of Sawyer was originally meant to be an older, slick, suit-wearing city con artist from Buffalo, NY. However, when Josh Holloway forgot a line at his audition and subsequently kicked a chair in frustration and loudly swore, the writers liked the edge he brought to the Sawyer character and decided to write Sawyer as more of a Southern, darker grifter instead.
The original name of Charlie's band was "The Petting Zoo". This had to be changed, however, when it transpired that there really is a band called "The Petting Zoo".
Yunjin Kim originally read for the character of Kate. The producers felt she was not what they were looking for in Kate, but decided to create a new character for her, along with a spouse.
Jorge Garcia, Matthew Fox and Dominic Monaghan all auditioned originally for the part of Sawyer as the other characters had not been developed yet.
Originally, Michael Keaton was cast as Jack. In the first draft of the script Jack was to be killed by the monster after they arrived at the cockpit. ABC told the producers that they shouldn't kill off the hero so soon in the series and the script was changed. After the change, Michael Keaton backed out of the role since he did not want to commit to a regular series.
Dominic Monaghan originally auditioned for the role of Sawyer, who was originally supposed to be a suit-wearing city con man. The producers were so enthused by Monaghan that the part of Charlie was altered to accommodate him - Charlie was originally going to be a 45-year-old washed-up rock star.
Originally Kate was supposed to have been a thirty something businesswoman whose husband had died in the crash. When Jack died in the original script Kate would have become the leader of the group.
Originally, Ilana was set to be Jacob's daughter, but the writers ran out of time to explain this plot, so they decided to kill her and focus on the big season plot.
In original drafts for the show, Rousseau's team of scientists were studying time. The network told the writers not to include it in the show, in case the viewers would think it too science fiction and stop watching.
Word of God: Now that the series is over, most of the burning questions fans have had will have to be/have been addressed in this way, if at all. Namely:
The original plan for Ilana's character (which may or may not count as canon) was that she would turn out to be Jacob's daughter.