Earth Drift

A work or series, most jarring if set in another world or universe starts out with many more ties to the real world than it later has. As the series goes on, re-viewing/reading/playing the oldest installments becomes disconcerting (if the reader is more familiar with the more recent installments) as a result of similarities to the real world being more frequent. Usually happens as a result of the work's mythology not being fully defined, or a Schrödinger's Gun that left a few traces of the original plan.

May not necessarily require the real-world references being in older works. This trope can still apply when you find a real-world reference in a newer installment and find it odd.

Subtrope of Early Installment Weirdness and typically a result of Continuity Drift. Related to Old Shame, Art Evolution and Characterization Marches On.

Anime and Manga

 * Pokémon has some of this trope. Real locations are mentioned, especially in the first generation games and anime. There is less real-world stuff in the later gens. Real-world animals including fish also appear less often later.
 * Also, in Pokémon: The First Movie, Mew is explicitly said to have been found in the rainforests of Brazil. Real life countries have never again been mentioned in the anime Pokeverse.
 * Let's Go, Pikachu! and Let's Go, Eevee!, quasi-remakes of the original games, excises many instances seen in the original. These include changing Lt. Surge from "Lightning American" to "Lightning Lieutenant", and changing an ex-Sylph Co. employee's reason for revenge no longer being that he was transferred to a "Russian no-man's-land" in Tiksi, and instead for a vague reassignment "off to the boondocks"

Comic Books

 * The Spirit was originally set in New York, but the location soon became Central City (ironically, at about the same time the less realistic objects like flying cars were removed).
 * Despite being a basically realistic police procedural in its early run, Dick Tracy began introducing more and more devices out of Speculative Fiction after the Second World War ended, starting with the two-way wrist radio. Eventually, the strip got so far into science fiction that a Dork Age ensued, and it was later brought back to Earth. Many of the gadgets stayed ahead of real-world technology until recently, though, with the heroes having miniature, internet-capable wrist computers decades before Blackberries and iPhones became commonplace.
 * The earliest Superman stories had him living in Cleveland, Ohio (the hometown of Siegel and Shuster). This disappeared within a few stories, and later stories had him resident in Metropolis ever since he came of age.
 * The first Judge Dredd story was set in New York, as opposed to Mega City One (which, to be fair, in The Verse's continuity absorbed New York, Washington, Boston and most of the eastern seaboard as far south as Miami until The Apocalypse War arc). Then again, the first story also included regular police within the justice department.

Fan Works

 * Undocumented Features started with a story about college students using a mysterious computer capable of manifesting physical objects to bring parts of their favorite fictional worlds into the real world. It's not until the fourth and final Core story that the entire universe is re-written to make all those fictional worlds part of the real world from the beginning, with even the protagonists forgetting that it was ever any other way.  For a reader who started on anything other than the Core stories, coming upon them (and other UF works set during them) can be confusing and disconcerting.

Literature

 * The first Redwall book has horses, dogs, references to most likely human harbors, and Portugal. All of those are gone in the subsequent books.
 * The first Fafhrd and The Gray Mouser stories by Fritz Leiber took place on Earth, before the world of Lankhmar was written into the series, with the result that when collected, some lines had to be added explaining why they were on Earth.
 * The first two books in the Kushiel's Legacy series are basically political thrillers with a bunch of Historical In-Jokes and bondage sex. Gods are an acknowledged presence throughout, but until the third book, they aren't much more than flavor to the Backstory. This escalates, however, through the second trilogy, culminating with the heroes of that trilogy founding a university to study magic, and the heroine of the third trilogy being quite explicitly magical.
 * The original version of The Gunslinger by Stephen King contains numerous hints that the book is set on Earth After the End, but later books in The Dark Tower series established that Roland's world was distinct from ours, and most of these hints were removed in the revised edition.

Star Wars and other Multimedia Franchises

 * For those who have only seen the special editions of Star Wars, it's weird seeing English writing on things like the tractor beam instead of the Aurebesh that later replaced it. It's also a little weird hearing Han Solo say things like "I'll see you in hell" in The Empire Strikes Back without the "nine Corellian hells" backstory. Of course, you can file such things under Translation Convention. Justified in Canon according to the Hyperspace Article "The Written Word" this is the High Galactic Alphabet. As for use of the Greek Alphabet that is also justified as the Tionese writing system.
 * Even in the remastered versions, A New Hope still contains standard numerals on screen as the Death Star nears Yavin IV. Although they don't match up with the numbers the characters are saying.
 * The original Marvel Star Wars tie-in comic run had many of these, with mentions of "Sunday school" by Han Solo (made even more curious since, for as detailed as the Expanded Universe got, it never actually named its months or days of the week), Jaxxon talking about "space carrots" (implying that there were places not considered to be from space—which would be assumed to be Earth), and so on.
 * The Ewok Adventure live-action TV movies had real-world horses and animals.
 * The Star Wars Holiday Special (which didn't directly reference Christmas, unlike the [thankfully non-canon] album) had many examples of 20th-century Earth technology (rather than merely the Schizo-Tech '70s styling later works would employ), ranging from eyeglasses, which are usually a rarity in the Star Wars Expanded Universe, to what appears to be a commercially available personal computer from the late 1970s.
 * The Thrawn Trilogy starts off by mentioning hot chocolate, of all things, referring to it as "exotic" and something Lando found in his travels.
 * A canceled novel trilogy was to explain how humans ended up in the Star Wars galaxy. Some characters who were descendants of the characters from American Graffiti and THX 1138 somehow travel to another galaxy and back in time to become the first humans in the galaxy.
 * American football is shown in the officer's club in one of the Rogue Squadron books. Corran Horn notes it as a strange sport he'd never seen before.

Tabletop Games

 * Magic: The Gathering currently has a defined multiverse setting, but it originally didn't. The first sets took place in Dominaria, but then there was an Arabian Nights-themed set, which was later retconned as taking place on the world of Rabiah. Also, older cards were more likely to have quotes from real-world sources such as William Shakespeare for their flavor text. This is still occasionaly done, but only in core sets, which don't have a storyline of their own.
 * Particularly, a rather confusing distinction had to be made due to an old card referencing "Dominia" instead of "Dominaria." The ultimate answer was that "Dominia" is essentially Magic's multiverse, though only this one, obscure card calls it such.
 * Exalted was originally the prehistory of the Earth (actually the Old World of Darkness). That's now ignored.

Video Games

 * Assassin's Creed - In the original, all of your targets are real people who actually died that year. Incongruity is explained by saying history is Written by the Winners. In the sequel, we get a truckload of Sci Fi in our farfetched Historical Fiction.
 * All of which was foreshadowed in the first game at various intervals, especially at the end.
 * The Elder Scrolls series has this as a Cyclic Trope. The first two games in the series, Arena and Daggerfall, while set in an unearthly world, were also similar to most fantasy RPG settings. Morrowind, the third game in the series and arguably better known than the previous two, is set in an entirely unconventional land, with nary a knight in sight. The fourth game, Oblivion, is set in Cyrodiil, home of the very Earth-medieval Empire. It can be strange going from seeing bizarre wildlife and random giant bug things in Morrowind to seeing realistic deer and wolves bounding across meadows filled with real-world plants. Even the mudcrabs become real-world crabs.
 * In Ratchet and Clank, Captain Qwark becomes a bizarre holdover, being the only human or human-like character in any of the games.
 * He has two fingers and a thumb on each hand. Whatever he is, he is definitely not human.
 * Super Mario Bros.. ended up losing any connection to Earth or Earth-like locations as the series went on. Note the 'realistic in comparison' settings of the original arcade Donkey Kong and Mario Bros.., then those of the later platform game series; then note how, after Yoshi's Island, the whole Fanon/manual-led Brooklyn thing got slowly retconned out of existence.
 * Warcraft I had references to God, hell and churches with crosses. Now they have been retconned into "the Light" and "the Twisting Nether".
 * In the original The Legend of Zelda and Zelda II the Adventure of Link, Link has a cross on his shield, which according to Word of God was added because the series was originally going to be based in the religion of Christianity rather than the three goddesses and the symbol of the Triforce in later games. A Christian-esque sanctuary appears in The Legend of Zelda a Link To T He Past, and both the NES original makes reference to a Bible ("Magic Book" in English translation) and a cross appears as a magical artifact in Zelda II. And as late as A Link To The Past, there is artwork of Link bowing down before a cross with Jesus clearly carved on it (especially weird because that was the game that introduced the Golden Goddesses).
 * Though such real world links were generally done away with by the time The Legend of Zelda Ocarina of Time came around, that game still features one notable example: the use of the star-and-crescent as the symbol of the desert-based Gerudo. Both newer versions of Ocarina Of Time and subsequent games replaced the star-and-crescent with a symbol that looks like the head of some insect.
 * Grand Theft Auto, since the III era. Grand Theft Auto III even had a reference to the then-fresh elected president George W. Bush; later installments had almost no real life persons. Then Grand Theft Auto IV comes out, which does away with even more real-life stuff - FBI is replaced with FIB, SWAT is replaced with NOOSE, all guns are AKA-47 now, and the president in 2008 was Joe Lawton, who is stated to be a buffoon whose father was also president several decades prior.
 * Pokémon Red and Blue make a large number of references to real locations and events. For example, a model of Space Shuttle Columbia and an NPC who discusses travels to the moon are present. It becomes an unnamed spaceship in the FireRed/LeafGreen remakes (which managed to keep intact every other real-world reference that no longer makes sense).
 * Inverted in Sonic the Hedgehog. It originally started in a very fantastic looking world, which later (coinciding with the 3D games) shifted to an alternate Earth.

Western Animation

 * The 2002 remake of He-Man and the Masters of the Universe never mentioned Earth, despite one of the original series' characters, Queen Marlena, being a human astronaut.
 * One preview for Cars actually showed Mater accidentally running over a bumblebee. Not a car colored to resemble a bumblebee, an actual bumblebee. In the final film, all animals in the Cars universe are also portrayed as vehicles.