According to a fan interview conducted with Todd Howard, a "Nobility" faction was originally present in the game and would have focused on the dealings of The Elder Council. According to Howard, "You made your way up and became "The Duke of Colovia" and sat on the Elder Council. The only remnant of that questline is the dead Duke in Castle Kvatch, which was to be the beginning of that line."

There's a disease in-game called "Ticklebritch" that typically goes unused in normal gameplay, but the DLC Mehrune's Razor provides a singular way to contract it. If the player picks up a certain hoe in Sundercliff Mines, they will contract the disease. Given that the only way to contract this disease is through picking up a hoe, this is likely a joke by developers alluding to STDs.

Unused voice lines for NPCs exist mentioning "Hearts Day" and "New Life Festival". These are both holidays that existed in The Elder Scrolls II: Daggerfall. It's possible Bethesda meant for the holiday system and these specific holidays to return in Oblivion, before being cut. Additionally, Pete Hines mentions in an interview that these holidays were to be present in an unreleased DLC.

Castle Skingrad seems to be modeled after Bran Castle, the castle famous for housing Dracula. In Oblivion, Castle Skingrad is home to Count Hassildor, a reclusive vampire who is featured in quest revolving around vampirism. The architecture is clearly similar, especially the spires of the castle, and is sits atop a hill outside of the city.

City-Swimmer incorrectly addresses herself as a "he" when referring to herself.

Icons exist for the Imperial Watch Armor, although there is no way to obtain it in-game (apart from the shield).

Icons exist for the Mythic Dawn Armor, but it cannot be worn as the items are classified as "bound items" and not equippable gear.

There exists an icon for the Dark Brotherhood rank of "Executioner", but the game forgoes it, promoting the player from "Assassin" to "Silencer".

The quest, "The Forlorn Watchman" features many references to the movie "Mutiny on the Bounty", which was based on the real-life event based on the ship of the same name. In the quest, the player must release a man's soul by releasing his body from shackles within a ship. Aboard the ship, the player discovers the mutiny upon the ship, led by a man named Gable the Traitor against their captain, Captain Laughton. In the 1935 movie, the captain is played by Charles Laughton and the "traitor" is played by Clark Gable.

A city named "Sutch" was cut from the final game. The only remnants are the existence of a "Fort Sutch" in the final game. Sutch is mentioned in lore throughout the series, and the E3 2005 demo of Oblivion featured Sutch on the world map.

Amantius Allectus' Diary, stolen during "May The Best Thief Win" may be a reference to the movie and musical "Little Shop of Horrors". The diary notes Allectus' cultivation of plants that feed on blood. He begins by feeding them cat and rat blood, but once he accidentally cuts himself on the plant, they begin craving human blood, which he then feeds them. In "Little Shop", the main character Seymour cares for a blood-thirsty plant who, once accidentally cutting himself on it, begins to feed it his own blood.

The quest, "A Shadow Over Hackdirt" appears to be a reference to the H.P. Lovecraft story, "The Shadow Over Innsmouth". The Lovecraft story tells of an investigator who travels to the town of Innsmouth, only to find it in shambles with few residents. The town is controlled by a cult of undersea creatures known as The Deep Ones. In Oblivion, the player travels to the dilapidated town of Hackdirt in search of a lost citizen of Chorrol, and finds a town in shambles with few residents. The main character soon learns the town is controlled by a cult underground known as The Brethren, with a book existing in the town entitled "The Bible of the Deep Ones". In addition, the Brethren feature large eyes unlike typical NPCs within the game. This may be in reference to Lovecraft's depiction of the residents of the town, "bulgy starey eyes".

The posters for The Arena in the Imperial City are a reference to the first Elder Scrolls Game.

The 2005 E3 demo video showcased a new system called "Radiant AI", which gave them general goals to achieve, how the goals were to be achieved was totally up on the NPC and the environment they were in.

This, however, presented problems when it was first implemented, as there were no "rules" for the NPCs to follow, only goals. This would cause many problems for the player including quest-lines being broken. Some examples are an unseen NPC going around town, buying up all the armor from the town stores, and another was an NPC important for the Dark Brotherhood questline would end up being found dead, as he was also a Skooma dealer and was killed by other NPCs needing the Skooma. As a result, many of the behaviors of the RAI had to be toned down significantly in the final release.

The NPC 'Jakben, Earl of Imbel' found in the Imperial City is actually an anagram of "Jack be nimble", from an old mid-19th century English nursery rhyme about a boy named Jack who would jump over candle sticks. He also owns a pair of unique boots important to the Thieves Guild questline which boosts the wearer's acrobatics skill by 50 points, allowing them to jump much higher than before. The name of the item, the "Boots of Springheel Jak", is itself a reference to a character from English folklore.

In the Spanish translation, the translation team mistook the verb "to train" (to work to improve skills) with the noun "train" (the means of transport), leading to the sentence "No hablar. No hablar. Solo tren." with "train" being the means of transport instead of the verb "entrenar".

A PSP version was planned for release around April 2007. According to Official PlayStation Magazine, it lacked the free-roaming game-play the games usually had, and felt more like a "dungeon romp."

Oblivion's main theme is used in a North Korean propaganda video.

In Oblivion, you can find a journal called "Macabre Manifest" which belonged to a grave robber. It includes:

Oford Gabings - Anvil

Travel Cloak with Silver and Green Leaf Fastener
Enchanted Shortsword with Inlaid Writing
Gold Ring with Inscription (Cursed?)
Leather Bound Travel Journal

This person is obviously a reference to Frodo Baggins (Oford Gabings is an anagram for Frodo Baggins, which further cements this reference) from Lord of the Rings. Upon completing the quest you receive a ring which looks very similar to the "Ring of Power".

The statue in Chorrol in front of the south gate is a rendition of the Pietà, one of Michelangelo's finest works.