Allohistorical Allusion

Allohistorical Allusion is a form of Lampshade Hanging or nod to the Fourth Wall used in Alternate History fiction where events, people, or jokes from real history ("Original/Our Timeline", or OTL) are mentioned in the Alternate Timeline (ATL). This is often done for the sake of tipping off the reader to the fate of someone important in OTL but insignificant in the ATL, such as taking the time to note that a certain German Corporal was killed in action in this timeline.

Can be in the form of a Historical In-Joke (in this case an Allohistorical In Joke), such as "I sure am glad that silly Rock & Roll fad ended" or "General MacArthur has been reassigned from the Philippines, but he swears he'll return". Can even be in the form of a misplaced pop culture reference: "Wow, I really didn't expect the Spanish Inquisition to attend King Phillip's court." Though this latter is arguably a traditional Historical In-Joke.

Another common form is more Meta: the fictional characters or fictionalized Historical Domain Character musing on What If things happened the way they did in actual history, such as President Lee of the Confederate States wondering what would have happened if he'd lost at Gettysburg. When done badly this can turn into As You Know.

Richard Nixon the Used Car Salesman is a specific subtype where a historical figure appears in a completely different occupation, same with Different World, Different Movies, sometimes.

Anime and Manga

 * In an episode from the first season of Strike Witches (which is set in an alternate 1944 in which aliens invaded and conquered most of continental Europe in 1939), Minna comments how if the aliens hadn't invaded, their superiors (Europe's political and military leaders) would likely be fighting among themselves. An episode from the second season (set in 1945) has the aircraft carrier Amagi supporting the Strike Witches in battle (in real life, the Amagi was a partially completed battle cruiser canceled under the conditions of the Washington Naval Treaty and was intended to be converted into a carrier, but was badly damaged in an earthquake and scrapped.)

Comic Books

 * In Watchmen, Robert Redford running against the incumbent Richard Nixon for the Presidency is met with derision, "This is still America! People don't want a cowboy actor for president!" In 1985 when it was written, the President was Ronald Reagan, who previously had a career as a cowboy actor.
 * Celebrating victory in Vietnam, the Comedian says that defeat would have "driven us crazy, y'know, as a country."
 * A more light-hearted example would be when Vice President Ford stumbles a little bit, when walking down some stairs.
 * How about those two Washington Post reporters found dead in a parking garage?
 * In the movie, the Redford joke is updated to "People don't want a cowboy as president," referring to then-current President George W. Bush.
 * Lampshaded by the fact that the first mention is a newspaper headline that refers to the candidate by the initials "RR".
 * In one Italian Disney comic, Mickey Mouse ends up in a parallel world where the Roman Empire never fell, though a lot of other things look like the late 20th century. As this alternate Earth has a science fiction genre, Mickey sets himself up as an author by repeating basic real world history as Alternate History. His first story of Columbus discovering America is severely edited, because "that's too unrealistic! It could never have happened that way!"
 * Early in Runaways, Mr. Yorkes uses a battle ax as a weapon and his wife refers to it as a "Samurai Ax". This seems to hint that the Yorkes have not only traveled through time, but have also visited alternate universes, since samurai are not known in this universe for using axes as weapons.

Fanfic

 * This happens routinely in James Ryan's Beatles fanfics on Rooftop Sessions:
 * "Carry That Weight" is about if Apple Corp. merged with Apple Computer. Apple Computer manages to become a monopoly in the early '80s because of this. At one point, John Lennon manages to drive some programmers, including Bill Gates, out of the Apple programming system. The narrator tells us than none of them were ever heard from again...
 * In "For Want of a Nail," in which Stu Sutcliffe never joined the Beatles, he is still alive and painting in 1966. Pattie Boyd is his artist's model on the day the story happens.
 * In the universe of the My Little Pony fanfic The Son of the Emperor Caligula placed his most trusted pony in the position of Consul. Because ponies are intelligent and sentient creatures capable of speech, his decision might have actually been a sensible one.

Literature

 * In one of Keith Laumer's Imperium novels, a mild-mannered fellow named Hermann Göring is delighted to learn that in the hero's home timeline he is instantly recognizable and has the dashing title of Reichsmarschall. The hero mercifully doesn't explain the context.
 * In Turtledove's Timeline-191 series where the South wins the American Civil War and the USA ends up in the Central Powers in WW 1, characters have a run-in with a certain German corporal who just seems to hate the Jewish character for no obvious reason.
 * Also in the series after the US Navy devastates the British Pacific Fleet in a surprise attack on Pearl Harbor in the British Sandwich Islands, a Confederate character calls the incident a "Day that will live in infamy".
 * There are almost uncountably many in Timeline-191; in a single scene in Return Engagement alone, we have a Jewish Congresswomen saying that Germany is too civilized to kill off its Jews, FDR saying that President Blackford was unfairly blamed for the Depression because he was unlucky enough to be in office at the time, and the characters discussing an Italian politician who "promised to make the trains run on time," but was never elected. On the humorous side, a young Ronald Reagan ("Dutch") is a popular football announcer, with his catchphrase, "There they go again!"
 * Turtledove loves this. In one of the "Tosev Timeline" stories (Worldwar (Literature)) he has a alien invasion craft's nuclear reactor get blown up and contaminate the surrounding area.... that area being Chernobyl. And then, later, a captured member of The Race is being interrogated by the Japanese and wishes that a nuke would fall on him. He is being interrogated in Nagasaki.
 * Played with in The Guns of the South, also by Turtledove; after losing the Civil War, Lincoln contemplates writing a book about what would have happened if "it hadn't been for Bobbie Lee".
 * One Wild Cards novel had a throwaway reference of The Beatles either suspected of or having mind powers. This was probably a Shout-Out to this real-life scare pamphlet.
 * And Fidel Castro being pitching coach for the Brooklyn Dodgers.
 * The historian Arnold Toynbee wrote an essay speculating on what would have happened if Heron's aeolipile and the Corinthian Diolkos were combined to give steam-powered rail travel in the second century BC. A brief mention is made of a failed prophet living at 4 Railway Cuttings, Nazareth.
 * One of the earlier Alternate History works, Winston Churchill's "If Lee Had Not Won The Battle of Gettysburg" in J.C. Squire's Alternate History collection If It Had Happened Otherwise (1929), used this as a framing device. Among the results if the Union had won, Disraeli might have become a Conservative and Gladstone a Liberal, Robert E. Lee might not have abolished slavery but prevented Negro enfranchisement, and a world war involving all the great powers might not have been averted.
 * The difference between the 'verse of the book Fatherland and that of the film of the book can be marked by a pair of references. The book includes a conversation that suggests that the Mersey Beat never left Merseyside. The movie has a Beatles poster up in Nazi Berlin.
 * ...which isn't all that relevant given that the book mentions a German critic blasting a Beatles performance in Hamburg.
 * Occasionally used in the Lord Darcy stories. Once, it's lampshaded when a character remarks that such an Alternate History might make a good sorcerous-fiction story.
 * There are several in Kim Newman and Eugene Byrne's Back In The USSA series of short stories. Including one where a character comments that something was as strange as finding London Bridge in the Arizona desert.
 * In "How I Lost the Second World War and Helped Turn Back the German Invasion" by Gene Wolfe, the Second World War only happens as a board game some of the characters are playing. The progress of the game includes several strange turns that the players remark would never have happened in real life, all of which are things that actually did.
 * Used in several of the stories in the The Mammoth Book of Alternate Histories: for instance Frederik Pohl's "Waiting For The Olympians" in which a science-romance author in a world where Rome never fell imagines what the world would be like if Tiberius had been Emperor; and Paul McAuley's "A Very British History", in which a review of a book about the Britain-dominated space program criticises the historian for wasting a chapter speculating on what would have happened if the UK hadn't got all the German rocket scientists after World War II.
 * The story "His Powder'd Wig, His Crown Of Thorns" by Marc Laidlaw takes it a step further; the alternate history depicted is wrong, and Magical Native Americans know how the universe should be (i.e. ours).
 * Robert Silverberg's "A Hero of the Empire" has the Roman main character speculating what the world would be like if he doesn't He does.
 * Resurrection Day by Brendan DuBois takes place in a United States turned into a Third World-type dictatorship after the Cuban Missile Crisis started World War III. A journalist talks of reading an alternate history novel in which the war didn't happen and JFK (reviled for supposedly starting the war) became a much beloved President. Needless to say there is no mention of Oswald. Other events include the protagonist reading a letter from his Dead Little Sister saying she was going to join a wonderful group that was going to change the world called the Students for a Democratic Society.
 * The Mirage, by Brian Ruff, features a version of the War on Terror where the roles of the Arabs and USA are reversed, so there are plenty of these. Perhaps the most entertaining is that Saddam Hussein, a gangster, also published several successful romance novels after Zabibah and the King (which here has a completely different plot).
 * In The Man in The High Castle, the novel-within-a-novel The Grasshopper Lies Heavy is alternate history about a world in which FDR wasn't assassinated. It turns out completely differently than in our timeline, but still with an Allied victory.

Live Action TV

 * The Alternate Universe in Fringe is home to a thousand and one of these. 20 dollar bills are called "Juniors" because of who's on them, and likewise Nixon is on the 50 cent piece and JFK is still alive, suggesting Kennedy's and Nixon's presidential wins might have been reversed.
 * A reference to the Lindbergh baby draws a blank stare (as, on the Other Side, the appropriate parallel is Peter).
 * Comic book history is starkly different, as well. Superman died in Crisis On Infinite Earths, the defining Darker and Edgier comic of the 1980s was The Man Of Steel Returns, the earth shattering comic book event of the early nineties was The Death Of Batman, and one of the most socially conscious books of its day was Red Arrow and Red Lantern.
 * The Other Marty starred in Back to The Future.
 * The Empire State Building still serves its original function.
 * And, in the moment that ended the first season, the White House has just finished reconstruction from the 9-11 attacks, and the World Trade Center still stands.
 * Aruba war vets.
 * Penn Station is now "Springsteen Station", suggesting that The Boss was just as popular over there, but had probably died.
 * And a hit musical Dogs.
 * And the Star Wars defense system is real thanks to the "Defense Czar" Walter Bishop.

Video Games

 * In the first Red Alert game, the Allies are suffering heavy losses and are being pushed farther West by the advancing Soviet forces. Then a new tactic is introduced by a German general that helps slow the Soviet advance and, eventually, pushes them back. The news report calls this new tactic "Lightning War" (Blitzkrieg in German). For those not familiar, the first game starts with Einstein violating Hitler's Time Travel Exemption Act and things kind of snowball from there.
 * Several other allusions in the series take the form of missions, including two separate "unheard of" attacks on Pearl Harbor (in 2 and 3) and a mission involving doomsday weapons in Cuba.
 * The map of Europe in the first game is a post 1990 map. You might think this is actually a mistake. It's just the perfect explanation for why Germany is in the Allies- the post 1945 settlement occurred in 1918.
 * One interesting example from Red Alert 3 involves an Allohistorical Allusion as Dramatic Irony: the unspecified "technology" the player is sent to recover in Soviet Mission 5, Mykonos, is pretty clearly nuclear fission, which hasn't been developed yet in this timeline. Dr. Zelinsky tries to warn the player that this technology "should" exist already, but doesn't due to their meddling, only to be very pointedly cut off by Cherdenko.

Web Original

 * Also very favorite in timelines from Alternate History Dot Com, like the Chaos Timeline and others.
 * The Reds! TL plays with this trope extensively.