There are eight Titanite Demons in Dark Souls, but the one on the bridge connecting the Demon Ruins to Lost Izalith is the only one that respawns due to a typo in that Titanite Demon's event ID. However, it's unknown if this was an accident or a deliberate typo to remove a limit from upgrading weapons.

Every environmental object in Dark Souls has an associated damage and health value, with breakable objects having a defense value of 0, 3, 90, 199, or 999 and unbreakable objects having an HP of -1. The player is only capable of destroying objects with defense values of either 0 or 3 such as boxes or tables while certain objects like the breakable wall at Sen’s Fortress, or the raised platform above the Asylum Demon at the beginning of the game, have higher defense values and can only be destroyed by enemies or hazards.

The Artorias of the Abyss DLC for Dark Souls was notoriously convoluted to access for newer players, requiring them to quit and reload their game in a cove at Darkroot Basin behind the Hydra boss to even start the sequence to get to the DLC levels. However, returning players had a better idea of how to access the DLC before it released by discerning the location where the levels are accessed through the DLC’s trailer and certain NPC dialogue.

The decision to add pigtails as a selectable female hairstyle in Dark Souls was the last request by a female graphic artist in the development team who had to leave due to an illness.

The large, exaggerated "eyes" on the Basilisk enemies are actually fake, and their real eyes are smaller and located just underneath.

During the development of Dark Souls, a popular tactic among the development team to go past Blighttown's Blowdart Sniper enemies (who can inflict the player with Toxic, a poison effect that gradually reduces the player's health) was to use the Dung Pie item to inflict Toxic on yourself already. This is because the Toxic effect from Dung Pies are much milder and the Toxic effect in general does not stack. This was not intended, but was kept in because they felt it added extra depth to the game.

According to director Hidetaka Miyazaki, Gwynevere's character design was inspired by a group of female characters from the 1974 Fujiko F. Fujio one-shot manga "Yasuragi no Yakata", about a stressed CEO who is directed to a members-only club by his doctor where men are dressed in children's clothes and cared for by giant motherly women who treat the men like infants as they regress further into baby-like states.

Gwynevere's extremely large breasts were added by the artist who designed her, who was reportedly so proud of his work that despite Miyazaki's standards, he did not have the heart to tell him to change the design.

Miyazaki also originally wanted to include a mouth on Gwynevere's palm and created animations for it, but this element was scrapped from her design.

According to director Hidetaka Miyazaki, the Crystal Ring Shield's "attack" is supposed to be based off of Ultraman's Ultra Slash attack from the Japanese television show of the same name. However, he has stated he was not entirely happy with how it turned out, as the artist he was explaining it to did not quite understand what he meant when trying to explain how it would look "like Ultraman".

There was originally a levelling system that allowed players to sacrifice their stats to restore their humanity. Each stat reduction would give the player four soft-Humanities each, with the limit being the base stats the player started the game with. The actual soul-level of the player does not reduce, possibly due to the system not being complete. However, the player could increase their stats without their soul-level increasing, up to the point of how many stat-levels they sacrificed. This would have made it a functional "Respec System", which would have allowed players to Reallocate their stats, albeit slowly.

Amongst all the hollow-corpses strewn across the game, there are only ten female hollow-corpses to be found. Nine of the ten bodies each refer to specific characters, some of them being summonable White Phantoms, four of them being Fire Keepers, and only one unknown female who is found holding Twin Humanities on their body in the Lower Undead Burg.

In the Artorias of the Abyss DLC, there is an NPC named "Marvelous Chester" in The Royal Woods. Like the chosen undead, Chester was pulled from his time period by Manus. Chester vaguely describes his era as Gothic/Victorian, his clothing also appears to be attire from the 19th century.

The character may have been included as a small hint as to what was coming up in Bloodborne.

The Crystal Lizard model from the previous From Software game Demon's Souls can be found within the game's files. It was likely used as a placeholder until a new model was made specifically for Dark Souls.

In an interview with the design team, the first draft for Kirk's Thorn Armor was going to be based off Hydra from the manga Saint Seiya: Knights of the Zodiac. Art designer Daisuke Satake and director Hidetaka Miyazaki didn't see eye to eye with the initial concept, as Satake's concept was "a huge guy covered in spikes", so they reworked it.

The final design began to take shape when Satake and Miyazaki began to talk about the Trial of 77 Rings from the manga JoJo's Bizarre Adventure, in which two characters had to earn their knighthood by defeating other combatants and wearing the rings they had on them onto their body, collecting a total of 77 of them. Miyazaki and Satake both liked the concept and decided to see what it would look like if the rings also had thorns on them.

Andre of Astora originally had a much different role in the early development stages of the game. He was originally going to be the son of Gywn and would also guard a door within the Fire Link Shrine, which he would physically move the goddess statue blocking it at some point in the game for the player. As development went on, his role was changed to that of a blacksmith.
His previous role as a guard of a door wasn't completely scrapped however, as he does hold the Crest of Artorias, which is needed to unlock the door to Darkroot Garden.

Knight Artorias (aka Artorias the Abysswalker) has cut dialogue found in the Artorias of the Abyss DLC. The cut dialogue implies he is not actually human himself and was slowly losing control over his own body and mind to the corruption of the Abyss, telling the player to stay away for their own good. In the final version of the game Spoiler:Artorias had already been completely overwhelmed by the Abyss, having no dialogue whatsoever.

The Brass Armor set which is worn by the Darkmoon Knightess was originally a starter-set for a class that was described as a "Pagan Knight." However, there was trouble with balancing it, so it was ultimately given to the Darkmoon Knightess found later in the game.

Using the Wrath of God and Force miracles, it is possible to deflect projectile spells and arrows if timed correctly. This can also be applied to deflect the bombs thrown by the Giant near the top of Sen's Fortress.

The Possessed Trees in Darkroot Garden have an unused attack animation, using their vines to swipe down at players. The idea of the trees attacking was likely left out because the developers wanted to trick players into thinking a path was blocked by a real tree and having to figure out to cut it down themselves, instead of attacking an enemy that is actively attacking them in order to unblock a path.

There are unused attack and death animations for the primordial serpents Kingseeker Frampt and Darkstalker Kaathe. At some point, they were intended to be killable but developers chose to make them immortal, likely because if Frampt Spoiler:was killed before transporting the player to the last location, the game would become unbeatable.

Crossbreed Priscilla has unused animations for standing and sitting. According to a developer interview, she was originally meant to be an ally of the player. As development went on, her initial role was eventually replaced by the Firekeepers. The unused animations were likely a remnant of her previous role, which are reminiscent of the Maiden-in-Black from Demon's Souls who was is a different location and position each time visiting her.