Warp drive of Star Trek fame already occurs in Fredric Brown's stories from the 1940s (the warp/fabric image of space-time probably dates back even earlier, from the first efforts to explain relativity to people who don't know about tensors).
Dr. McCoy's famous line "I'm a doctor, not a _____!" from Star Trek actually originates in the 1933 film The Kennel Murder Case, where a coroner insists repeatedly "I'm a doctor, not a ____!" (reporter, detective, etc.).
The reintroduction of the Cybermen in the new Doctor Who story "Rise of the Cybermen" prompted some claims that the monsters were a rip-off of Star Trek's Borg — in fact, Doctor Who fans had been making exactly the opposite claim ever since the Borg were first introduced more than 20 years after the Cybermen first appeared in the 1966 story "The Tenth Planet".
Doctor Who: "You belong to us. You will be like us."
Star Trek: "You will become like us. You will service us."
Doctor Who: "Resistance is Useless" (September 1967)
In the Star Trek franchise, the Vulcan salute, and its accompanying farewells, "Peace and long life" and "Live long and prosper", are both derived from Jewish benediction services. (This was confirmed by Leonard Nimoy when he hosted a retrospective on Star Trek in the early 1980s.)
(Cf. Deuteronomy 5:32-33)
The concept of a virtual reality called "The Matrix" was used earlier in Doctor Who in the 1976 serial "The Deadly Assassin", twenty three years before its better-known movie namesake. The concept was first used in Simulacron 3, a novel by Daniel F. Galouye, written in 1964.
In-fandom, when new series fans gush over the genius of some ideas and concepts without realising many of then existed in the old series. So horror elements written by Robert Holmes (half of which he borrowed from old horror movies anyway) and later reused by Russell T. Davies or Steven Moffat are seen as their "genius". Even if the writers have themselves, and to their credit, frequently acknowledged that some of these elements are tributes to the writers whose stories they grew up with (there are very few cases of Davies or Moffat blatantly taking credit for major characters or concepts that originated in the original series; media that refers to Davies as the "creator" of Doctor Who are simply clueless). Of course, the most extreme example of this is when new series fans preface their fanfics with "Doctor Who belongs to Russell T Davies and/or Steven Moffat"...
The inverse is also true; if you want to base your criticism of some plot point on the claim that nothing like it would ever have happened in the original series, you'd better make damn sure it didn't. It's worse than that, for some fans of the new series. Upon being informed that there was a show prior to 2005, they will balk and call you a liar, and dismiss the evidence as being made up.
Or, alternately, they will actually stick to the opinion held by some diehard fans of the classic series that the 1963-89 and 2005-present series are completely different shows, even though rock-solid connections were established within the first few weeks of the revival.
The idea of the Doctor's history being changed leading to a chaotic world has been used in Turn Left and The Name of the Doctor. Sounds like a great and original idea? Actually it was used in the Doctor Who Magazine comic "Time and Time Again", made to celebrate the 30th anniversary in 1993. Here the Black Guardian prevents the Doctor from leaving Gallifrey, leading to various creatures fighting over Earth.
"The Name of the Doctor" gets a lot of this, also taking elements from "Alien Bodies", "Unnatural History", "The Room with No Doors", and "Timewyrm: Revelation". In fact "Timewyrm: Revelation" has inspired a lot of other stories.
The episode "Dalek" was widely credited with making the Daleks scary again after a fairly lengthy period of having undergone Villain Decay; in particular, it demonstrated that the Daleks could actually fly, in reaction to the standard joke of the best way of defeating Daleks being to climb a flight of stairs. In fact, several of the elements that "Dalek" apparently 'introduced' to the Daleks — including flight — actually originated in the 1988 serial "Remembrance of the Daleks".
A lot of elements of New Who came from the Doctor Who Expanded Universe such as a robot duplicate of a companion living for centuries, a time rift in a major city.
A Doctor Who story where Humans are the real monsters? Sounds like something from New Who? That was done in the first story featuring a meeting between humans and aliens (not counting the main characters), the eighth story "The Sensorites".
You still see people claiming that WKRP in Cincinnati was inspired by the 1978 film FM. In fact, the WKRP pilot was filmed months before FM was released.
A beautiful, intellectually unremarkable young woman befriends and comes to rely on a group of brilliant-but-awkward geniuses who work at a university, one of which develops a crush on her. The Big Bang Theory, right? Wrong — it's a movie called Ball of Fire, released in 1941 and starring Gary Cooper and Barbara Stanwyck.
Much has been made of how innovative the format of Law & Order was when it first debuted, but there were two obscure earlier shows that had essentially the same structure: Arrest and Trial (1963-64) and The D.A. (1970-71).
The middle section of Babylon 5 — the part with Nightwatch and the Ministry of Truth — has been accused of being an Author Tract against the War on Terror and the Bush Administration in general. The last episode aired in fall 1998, almost three years before 9/11.
In-universe example from Dexter. When the Bay Harbor Butcher sent a manifesto to a newspaper, Batista noticed a literary reference:
Batista: "You can't depend on your eyes when your imagination is out of focus." Masuka: He's a Trekker! That shit's straight from Deep Space 9. Batista: What? Mark Twain said that. It's one of his most famous quotes. Other officer: Twain was never on Deep Space 9. He was on Next Generation. Batista: He didn't say it on Star Trek. Other officer: Okay, so what's it from? Lundy:A Connecticut Yankee in King Arthur's Court.
In 1969, a new comedy sketch show debuted that completely tore apart the format of traditional sketch comedy, replacing conventional sketches with sketches that simply stopped mid flow, sketches that ran into each other and a whole lot of silliness. It is Spike Milligan's Q series which preceded Monty Python's Flying Circus by a few months (to be fair, the Monty Python team were working on their show at roughly the same time). The Pythons acknowledged The Goon Show as a major influence, so it's unsurprising that Flying Circus would bear similarities to another work of Milligan's.
Q5 started just as Python had been given their show but didn't really have a concrete idea of how they were going to accomplish what they wanted with it. It's mentioned in interviews and in Michael Palin's diary that there was at least one conversation between them about how they'd seen Q5 and thought, "That's what we were going to do, isn't it?"
"Four Yorkshiremen" did not originate with Monty Python. It was from At Last the 1948 Show, and the original performers were John Cleese, Graham Chapman, Tim Brooke-Taylor, and Marty Feldman. Tim Brooke-Taylor, known from The Goodies, has said that people refuse to believe he co-wrote the sketch. (He tries to tell that to young people nowadays, and they don't believe him.)
Mighty Morphin' Power Rangers was often called a "ripoff" by uninformed Voltron fans due to the similar design of the Dino Megazord, unaware that both series were Americanized adaptations of Japanese shows and that the Super Sentai franchise that Power Rangers is based on is a year older than the franchise to which Go Lion, the Japanese version of Voltron, belongs. Also, both shows were made by Toei.
Although, Toei does acknowledge that the Dino Megazord's design (technically the Daizyujin from Zyuranger) was made as a homage to Voltron (Go Lion). Source in Japanese.
It's also common for fans of Power Rangers to later discover Voltron and mistake it for an animated ripoff of the former.
Some Power Rangers fans who later discover Super Sentai accuse the latter of being ripoffs of the former.
Calling anyHenshin Hero related property a ripoff of PR, as if the Toku genre wasn't, well, a genre (and as if we haven't been hearing the word "Shazam!" since The Forties.)
With the Vampire Diaries TV adaptation airing in the midst of the Twilight-craze, many twitards believed Vampire Diaries stole most of its elements from Twilight. The Vampire Diaries books were made in the nineties. It is not an unreasonable suspicion, however, that the popularity of Twilight had something to do with the Vampire Diaries being adapted now. The TV show is virtually In Name Only in relation to the Books though, and many changes did undeniably make it more similar to Twilight (though those things being unchanged would have encouraged even more comparisons to Buffy the Vampire Slayer).
A similar phenomenon occurred with True Blood. The Sookie Stackhouse books were written a couple years before the Twilight novels, and True Blood premiered about two months before the first Twilight movie. Although it is likely that the popularity of Twilight did have something to do with the timing of the adaptation.
There are those who think TV series based upon vampire culture is a recent innovation, but True Blood and Vampire Diaries are only recent examples of the genre. For example, there was Kindred: The Embraced in 1996, Moonlight, and Forever Knight, to name a few, not to mention, of course, the Buffy/Angel franchise launched in the early 1990s. And before any of the above was Dark Shadows — not a stupid film starring Johnny Depp, but a 1960s soap opera that featured a vampire named Barnabas Collins as its dark and brooding protagonist. It was revived decades later in the 1990s.
Some people are now accusing the series Arrow of being a rip-off of Hawkeye from the movie The Avengers. This is despite the fact that Arrow is based off Green Arrow, a comic book character who predates Hawkeye by over two decades (and who arguably Hawkeye was influenced by). And was a regular on the same channel's previous superhero show Smallville, by the by.
Alan Alda's depiction of Hawkeye Pierce in the TV version of Mash borrows heavily from Groucho Marx, to which a nod was made in the first-season episode "Yankee Doodle Doctor". By way of sabotaging an attempt by Army brass to propagandize the 4077th's "heroic doctors", Pierce plays Groucho in the Movie Within The Show, and Trapper John plays Harpo.
When the Canadian show Ed's Late Night Party aired for a short time in the US on G4, many viewers criticized Ed the Sock for ripping off Triumph the Insult Comic Dog. Ed the Sock had actually been around on various Canadian programs since the early-90's and was possibly an inspiration for Triumph. This led to Ed resenting Triumph, and NBC insisting that the character shouldn't be anywhere near Conan's show when it taped a few episode in Toronto. Ed the Sock was scheduled to appear on Conan O'Brien but cancelled at the last minute. Three months later Triumph appeared on the show.
In-universe example in Wizards of Waverly Place. Max has claimed his name is Tom Sawyer so his girlfriend doesn't know he's related to Alex.
Alex: That is such an obvious lie. It's the name from the Rush song.
Harper: And the classic book.
Alex: Wow. That song was good, I didn't know they made a book out of it.
Rod Serling wrote The Twilight Zone episode "The Silence" without knowing that it was virtually the same story as Chekov's The Bet. There is an interview with Serling in the DVD set for the series in which he explicitly explains all about it.
The classic Disney cartoon Lonesome Ghosts, in which Mickey, Donald, and Goofy portray ghost-hunters decades before either the TV show or the movie. The little known Disney Channel original series DTV even lampshaded this fact by running a video in which scenes from that cartoon are shown with the Ray Parker, Jr., theme song from the movie playing in the background.
When the series premiere of The Walking Dead first aired, some viewers immediately accused the show of ripping off the "protagonist wakes up in a hospital after a post-apocalyptic event" scene from 28 Days Later, which was released a full year before that, in 2002 throughout the UK and Europe although it did not see wide distribution in the United States until June of 2003. In fact, not only did the comic book series show this scene a full seven months before 28 Days premiered in theatres, but both of those films copied it from The Day of the Triffids, which was written in 1951 (more than 50 years before either of the two works in questions).
The 1949 book Earth Abides begins with a similar instance. The main character, Isherwood Smith, is bitten by a rattle snake and rendered insensate but immune to the apocalyptic plague that begins the story. When he recovers, he has no idea of what happened and is confused to find deserted towns only piecing the story together through newspapers.
The practice of following an episode with a preview that shows clips from the next episode didn't start in the '80s or '90s. Some film serials did the same thing at least as far back as the '40s.
Here's a good one: Jon Stewart occasionally does a nasally, weasely voice on The Daily Show that many young viewers associate with his show (for an in-television example, Britta Perry does so on an episode of Community). However, older viewers will recognize it as a reference to a Johnny Carson voice / character, one that Johnny often went to when a joke fell flat ("Whoa, bomb-o!"). But here's the kicker, even older viewers will know that Johnny's voice was originally a reference to Jackie Gleason's Reginald Van Gleason III character ("Mmmboy are you fat!", as mentioned in an episode of the Sopranos).
Years ago, there was a critically acclaimed British mini-series about the Julio-Claudian dynasty of Roman emperors, shot entirely on studio sets, with a script drawn from such classical sources as Tacitus and Suetonius and featuring a cast composed largely of classically trained stage actors, with particular attention paid to the lame, stammering Claudius' unexpected rise to power. The series was... Granada Television'sThe Caesars, which preceded the more famous BBC adaptation of I, Claudius by eight years. (Of course, the books by Robert Graves from which I, Claudius was adapted were older still, and may have influenced the scripts of The Caesars.)
Ever since the mid-1980s, Jeopardy! and Wheel of Fortune have been fixtures on nighttime syndicated television — two Long Runner game shows that are often paired, extremely well-known, often paired with each other, and not going away anytime soon. However, both of them are older than they let on.
The current, Alex Trebek-hosted Jeopardy! began in 1984 as a revival of a show that originally aired from 1964 to 1974 with Art Fleming as host; Fleming also helmed a short-lived revival in 1978-79. (The 1960s version is spoofed in "Weird Al" Yankovic's "I Lost on Jeopardy", which predated Trebek's version by a few months.)
Wheel was continuous. It began in 1975 as a daytime show for NBC hosted by Chuck Woolery and Susan Stafford — current host Pat Sajak took over in 1981, and Vanna White almost exactly a year later. Pat and Vanna made the leap to nighttime in 1983, hosting both daytime and nighttime until Pat stepped down from daytime in 1989. Daytime ultimately fizzled out in 1991 after two host changes and two Channel Hops, but nighttime is still locked firmly in place with Pat and Vanna. In Wheel's case, it doesn't help that the show constantly references what nighttime season it's on, and that Chuck Woolery would become more famous for his later work on Love Connection, Scrabble, and Lingo.
Speaking of Lingo… for most of the 2000s, it was a fixture on GSN, and arguably its most successful original game show. It was a revival of a little-known 1980s show that died off because its financially-troubled parent company wasn't able to pay contestants their winnings.
And possibly more extreme than Jeopardy! or Wheel of Fortune is The Price Is Right, which began in 1972 as a heavily-souped up version of a 1950s game show hosted by Bill Cullen. The 1950s incarnation was far simpler, but still based around bidding on prizes.
Tic-Tac-Dough is most known through its 1978-85 version, which spawned Thom McKee, once the biggest winner in American game show history. It was a revival of a 1950s game show.
If you say Match Game to an average television fan, they will most likely think of questions pertaining to Dumb Dora, the snarky interactions of panelists Brett Somers and Charles Nelson Reilly, every third question having the answer "boobs", and a bright orange shag carpet set for the ultimate in The Seventies appeal. That was a revival of a far more formal 1960s game of the same name, and the creators didn't flip the Silliness Switch until about a year into the revival.
Even older than that, actually. Dan Castellaneta based the noise (rendered in scripts as simply "(annoyed grunt)") on an actor from old Laurel and Hardy films, the latest of which was from 1940.
Many people think that Lexx is a cheap ripoff of Farscape, when actually Lexx aired 2 years earlier (albeit not on American TV).
An in-universe example in Sleepy Hollow: It turns out Ichabod doesn't need the term John Doe explained to him because it originated in England long before his time. It may go back as far as the 14th Century.
Eureka has an in-universe example. Carter mentions the telephone as a modern convenience that time traveler Trevor Grant would miss if he went back to the 1940s. Grant points out that it was invented in 1876.