Beam Me Up, Scotty!: People quoting Andre's parting words to player often cut his two lines down to "Don't go turnin' Hollow."
Bilingual Bonus/Multiple Reference Pun: At the end of the prologue, the player is carried to a different part of the world by a giant crow, which many suspect is in some way related to Velka, the goddess of sin, who is associated with crows in the lore. In Czech, the word "velka" is a feminine form of "velky", meaning "large". The word for "crow", "vrana", is feminine, meaning that it's used with the feminine form of adjectives. A "large crow" is therefore "velka vrana".
Breakthrough Hit: Demon's Souls was a Sleeper Hit and a slowburner that slowly built up in popularity through good word of mouth and critical acclaim in the west. Dark Souls on the other hand was an instant hit, selling 1.6 million copies within the first month, 2.367 million by 2013 and helped put From Software, a Japanese developer with a small cult following in the states, on the map as a developer of great, hardcore titles. It was also a Breakthrough Hit for director Hidetaka Miyazaki, who was only credited in three games before he got notoriety for his work with Dark Souls and Demon's Souls. Even he was shocked by how much press and requests for interviews he suddenly started getting. Not bad for a niche title from a small developer.
Colbert Bump: The Silent Comedy received this when their songs, Bartholomew and All Saints Day, were featured in a couple of trailers for the game.
The two Souls games also help spark up interest in FromSoftware's King's Field series, which never caught on in the states.
And then Colbert himself mentioned playing it during an episode...
Dueling Games: Despite being a month apart, Dark Souls has a rival in The Elder Scrolls V: Skyrim, with both being the top RPGs coming out in 2011's fourth quarter. Fans of both series groaned at news outlets trying to play up this conflict in spite of the games' numerous differences.
Darkroot Garden and has been dubbed Dickstab Garden due to Forest Hunters constantly invading players. Forest Hunters themselves are sometimes called "Park Rangers" for the same reason.
Sunbro and Brolaire for Solaire of Astora due to him being a great help in boss battles and Onionbro for Siegmeyer of Catarina due to his helmet looking like, well, an onion. The Sunbro nickname has spread to all the players that joined the Warrior of Sunlight covenant, as that puts an emphasis on "jolly cooperation!" Players also glow a bright gold, the same as Solaire has. Siegmeyer's daughter is often called "Onionsis" by association.
In a similar vein to Solaire and Siegmeyer, Laurentius of the Great Swamp has been referred to as Swampbro and Pyrobro.
Wolfbro, for Great Grey Wolf Sif.
Siegmeyer (or mostly anybody wearing the Catarina set) is known as Onionbro.
Gravelord Nito has been referred to as Papa Nito. Members of the Gravelord covenant are often called Waitlords, in reference to the fact that Gravelording consists of a lot of fruitless sitting around waiting for players you're infected to invade you. Alternatively, this waiting-created boredom combined with the ability to dance (thanks to the Channeler's Trident) have inevitably lead to the name Ravelords.
Lautrec is know as Yurt 2.0 and Gold Yurt considering the way you meet him and what he does after you free him.
Anor Londo is called "Anal Rondo" or "Anal Rodeo" by some, in reference to its difficulty (especially the bridge part with Silver Knights firing javelins at you).
The official guide refers to the unseen crow NPC in the Undead Asylum as Hawk Girl, but Sparkly and/or Snuggly are more popular.
Sen's Fortress can be "Sen's Funhouse," or, as the result of a humorous typo, "Super Nintendo Fortress."
Estus is often called Sunny D, because an Estus Flask that still has uses is roughly the same color and shape as a half gallon of the drink.
Members of the Darkwraith Covenant are commonly referred to as "Dickwraiths". In a similar manner, members of the Darkmoon Covenant are sometimes referred to as "Dorkmoons".
Due to one of Knight Artorias' attack in which he throws a liquefied... something of the Abyss that looks like dark blue/black ink, he is sometimes called Knight of the Oil Spill.
In Japan, Xanthous King Jeremiah's infamous turban is nicknamed "Borraginol", after a brand of suppositories sold in Japan. Some Let's Players even go so far to include the Borraginol jingle (cheerfully saying "Borraginol for your hemorrhoids!") when they use the armor.
Flip Flop of God: According to the Dark Souls Official Guide, the Bed of Chaos Guardian's real name is Quelaana, which would fit right in with the prefix convention of the Chaos Sisters (Quelana of Izalith and Quelaag). However, the guide also describes the Bed of Chaos Guardian as a male...
Although considering that the translators were working with enemies without any real official names, just in-studio concept names that the development team would refer to enemies as for ease of discussion, mistakes like that were easy to make.
Hey, It's That Voice!: A few voice actors from Demon's Souls return to voice different characters. For example, Frampt and Kaathe are voiced by Peter Marinker (King Allant), Quelana is voiced by Jenny Funnell (Yuria) and Priscilla is voiced by Clare Corbett (Astraea). Alvina is voiced by Judi Dench soundalike Ève Karpf, who, fittingly, voiced M in some of the James Bond games, as well as Minerva McGonagall in the Harry Potter games and Lara Croft's mother in Tomb Raider Legend.
Artorias was voiced by Josh Cohen who played Ostrava from Demon's Souls, but the files were eventually dummied out and left unused. However, data mining in the PC version found them. Prepare to Cry.
Shrug of God: Director Hidetaka Miyazaki's stance on whether the pendant has any secret use in game, though he encourages players to keep looking.
Teasing Creator: Miyazaki is like this; he doesn't say if the pendent has any secret use, but encourages players to continue looking. He states that Ceaseless Dicharge is skippable (He is), before mysteriously stating that maybe he isn't (some of the equipment used to make that run was later nerfed, so it may no longer be possible).
Throw It In: Surprisingly enough, Maneater Mildred. Word of God says that one of the developers invaded during debugging and surprised the rest of the development team. They liked it enough that they got the data and quickly wrote up a background for her.
Trolling Creator: When the game was released, game director Hidetaka Miyazaki hinted that the pendant you could choose as a starting item would be a Chekhov's Gun. A year later, Miyazaki later admitted that the pendant is completely useless since the whole thing was intended as a prank. So basically, Miyazaki tricked hundreds or even thousands of players into choosing a completely worthless pendant as their starting item!
Even better is the nature of this prank. Players would only have to see it to believe there was some use for it, and from there came an endless stream of theories. For that to happen, all that had to be done regarding the Pendant is it had to be in the game, and the very nature of Dark Souls as a game did the rest. Miyazaki played a very elaborate prank by simply putting the Pendant in the game.
Urban Legend of Zelda: Since the game's release there have been dozens of different rumors pertaining to the Furtive Pygmy and the true purpose of the Pendant.
Another persistent rumor claimed that the player has the option to spare the Great Grey Wolf Sif and that you would get his sword as a reward for doing so. No proof or method has been found, but many still believe there is a way to accomplish this. It is possible to technically spare Sif, by using a certain glitch to transfer the Covenant of Artorias to a new character. You get no proper resolution for it, of course.
Quelaag originally had a rather long intro speech which ran from when you entered her domain to when you entered the fog gate for the boss battle. But Miyazaki felt that the script for it was of poor quality and that it took something from her character.
Priscilla was originally supposed to be a major heroine, akin to the Maiden in Black from Demon's Souls. Due to her original role becoming obsolete with the addition of the fire keepers, she was placed in the Painted World of Ariamis due to the location's winter atmosphere.
On top of that The Painted World of Ariamis that was used for Priscilla was the actual basis from which the Project Dark prototype was turned into Dark Souls. Gravelord Nito was originally supposed to be the area boss instead of Priscilla, with the latter's boss arena actually being a crumbling floor, much like the Stray Demon. After spending so much time creating the area for the prototype, Miyazaki was determined to include it in the final product, but couldn't do it coherently in accordance to the rest of the game world. So he ended up "cheating" and created the Painted World.
The knight that gives you the Estus Flask was originally named Oscar and was intended to be your rival throughout the game, siding with whichever serpent you didn't, instead of dying when you reach up to him after the Asylum Demon. The name used in the strategy guide is the only holdover from this incarnation.
Andre was originally supposed to be a descendant of Gwyn and more imposing, serving as the guardian of the door to the Firelink Shrine. He was also supposed to move the goddess statue found in the ruined temple, allowing the player to progress with the story.
Content that was cut from the game reveals that entering into a Covenant with Velka would be possible. Said covenant was quite possibly merged with or was turned into the Darkmoon Covenant.
When Smough was first conceived, he was originally supposed to be one of the Four Knights. Miyazaki allegedly liked him so much he decided against making him a knight and worked it into his backstory as a heretic who wished to join the Four Knights.
There was Concept Art of Abyss Walker Artorias drawn for the game, indicating he might have made an appearance at one point. He appears in the Updated Re-release, albeit with a different character design than his original.
Gwynevere was based on a character from a manga called Yasaragi no Yakata, or Tranquil Mansion, where members of an exclusive club would have a giant woman care for them as if they were children. One idea was that she would lower her hand for the player character to kiss, there is even animations for it, but the idea was scrapped. She was originally going to be more lithe and elegant looking compared to the... voluptuous version that ended up in the game. The artist who designed her was so proud of the concept art when he showed it to Director Miyazaki that the Director couldn't bring himself to reject the design.
Firelink Shrine was supposed to be a water temple: a very healing locale with water, greenery, soft light, and subtle music. As the idea of Kindling and Frampt's arrival developed, the water eventually dried up to what is seen in the final product. Even the bonfire was moved, since the uneven ground of the original placement interfered with the player's sitting animations. The finalized location was originally a small pond.
The boss fight atop the Undead Parish was originally the Demon Centipede, but due to how ridiculous it seemed, the Centipede was moved and replaced with the Gargoyles.
Oswald of Carim was originally supposed to be a woman of age 60, and you were originally supposed to use an Affidavit item, similar to the Indictment item, to leave your current Covenant instead of being able to straight-up ask to him.
By hacking the game and making the debug menu available, one Dark Souls fan found some very interesting character models that were dummied out of the final game.
Of these include an undead clad in bizarre gold armor named "Undead King Jar-Eel◊", a darkwraith with the power of life drain who would have been the boss of New Londo. The Four Kings use a portion of his coding, and even appear to be wearing a corrupted version of his armor. Presumably, he was removed for being too similar to Gwyn, (a tall, humanoid enemy which has become a husk of his former self). Ingward was also supposed to sic him on you as a test to prove whether or not you're worthy of entering the Abyss.
There's also an alternate Bed of Chaos that appears to have been designed as a more traditional boss fight with crawling and jumping animations. Word of God says that the original Bed of Chaos was supposed to have a stronger boss fight concept, but instead became the relatively simple-but-irritating Puzzle Boss due to time constraints that kept the concept from being properly polished.
There are also a few unused enemies like the Brain Bugs and the Claw-Hollows, which we saw fan art for but were never seen in the final game.
A dummied-out "side quest" had you rescuing Petrus from the necromancers of the Catacombs to start his and Rhea's character arc, instead of being able to encounter him from the get-go and starting the arc via ringing the first Bell of Awakening. Although it may have been cut to keep aware players from figuring out his intentions as easily.
Shiva was supposed to be something similar to what happens with Lautrec: he would attack you if you either showed him the Chaos Blade - in an attempt to take it from you - or gave it to him, in an attempt to test it on a worthy opponent. This would also serve as a Call Back to Demon's Souls, in which Master Satsuki would attack the player if they showed him the Magic Sword "Makoto" (or would attack them if they voluntarily handed it over to him). In addition, he was also supposed to be invaded in the Painted World with a Black Eye Orb (as with Lautrec) in order to re-obtain the weapon. The scripts for the invasion is still in the game, but are unimplemented.
Dusk of Oolacile was originally supposed to summon you to her world in order to rescue her, rather than freeing her from the golem. However, the dev team didn't take the concept seriously, and the idea was scrapped. The Artorias of the Abyss content was 99% rebuilt from the initial idea, but a small number of things are still in the game files.
An alternate version of Kalameet that had a different appearance, unique attack animations, a tail that couldn't be severed, and he was supposed to be a more airborne opponent with the same range of movement as the Belfry Gargoyles. He even had a unique stagger animation for if he was felled from being airborne.
A few early versions of Marvelous Chester exist. One version that looked more like his concept art from the Collector's Edition art book and two versions that were sans his top hat and longcoat that wielded a black-bladed zwiehander.
An early version of the Sanctuary Guardian that breathed fire instead of lightning. This version was to be an enemy encountered in Blighttown, the Demon Ruins, and Lost Izalith. The "bounding demons" (a.k.a. the ass ends of the Undead Dragons) found in Izalith may be replacements for this version of the Sanctuary Guardian.
The triple-shot crossbow Avelyn was originally supposed to belong to Domhnall of Zena before the developers turned it into an elusive treasure.
There are a number of unused animations still in the game files:
A number of animations for Anastacia from when she was outside of her cell - a talking cycle, a damage cycle, a death cycle, and a "rebirth" cycle.
Andre does not have a typical idle cycle, but had a talking cycle where his mouth moved. He also had a transitional cycle where he would put away his hammer before attacking if he was attacked.
Priscilla has only two animations - a sitting animation and an animation where she stands up.
The Ancient Dragon had a number of animations that indicate that it could have been an enemy.
Frampt/Kaathe have a number of attack animations.
Chester had a sitting animation, a sitting damage animation, a standing animation, and an animation where he is using an item.
Gwyndolin had different damage animations, a knocked-down animation, a sitting animation, a sitting damage animation, a standing animation, and different movement animations.
Gwynevere had a talking animation, an animation where she puts her hand out, a talking animation for that pose, and an animation where she draws her hand back toward her. The hand movement animations are tied to a cut idea, where the player character would kiss the back of her hand. Interestingly, during all four animations, her eyes are open and she blinks, and she her mouth moved during the talking cycles.
Rumor has it that the "Final Death" idea from Demon's Souls was to make a return in Dark Souls. After the player character had died a certain number of times, they would have Hollowed and that particular save file would have been either locked or deleted.
Word of God: Developer interviews have shed some light on the story of the game.
Miyazaki has stated that the Pygmy is the ancestor of humanity and that humanity inherited a piece of the Dark Soul through him.
The Gaping Dragon was originally a normal Everlasting Dragon that became corrupted by its own gluttony, causing it to grow a massive maw.
Ceaseless Discharge is confirmed to be the brother of the Daughters of Chaos.
If you kill Gwyn with Solaire as a phantom, Solaire links the fire in his own world.
Kirk is a member of the Chaos Servant covenant.
The ruins in Darkroot forest were originally part of Oolacile. Combines with What Could Have Been. You were originally supposed to be summoned there to rescue Dusk. The Updated Re-release builds on the cut content.
The Crow Demons found within the Painted World are followers of Velka, whom had their wish to grow wings and fly transmogrify them into the beings encountered.
Writing by the Seat of Your Pants: Like many other video games, story comes after the game. Miyazaki has said in interviews that he makes up the lore as he goes along.