Redundant Parody

Parodies are hard to write if you're unfamiliar with the original work. Sometimes, you'll make points that the work itself refutes. Sometimes, you'll treat tongue-in-cheek works like they're serious. But some spoofs make an even more serious error. They try to mock the original work with their own humorous spin but reproduce the original instead of parodying it.

The original included the same material, either as a self-aware joke, which renders the parody superfluous, or as a serious plot point, which invalidates the parody's argument. People unfamiliar with the original may laugh at the joke, but others will be put off by the spoof writer's ignorance and the redundancy of the resultant parody.

Some comedy writers avoid this trap by limiting their targets. Riff Trax refuses to mock comedies, fearing their commentary will sound too much like the original.

Anime & Manga

 * In Spain, saying you're "turning black" means you're getting angry, much like a video game boss Turns Red, but black. A Dragonball parody comic had Mr. Popo (Who is black) say he was "turning black" as a joke... except he actually says that on the Spanish anime dub at one point.

Comic Books

 * Early in Marvel Comics' parody What Th--?! series, writer-artist John Byrne penned a story in which Superman and the Fantastic Four meet. After the Thing shows up, Byrne adds a footnote saying, "I'm sorry, it's impossible to write parody Thing dialogue that doesn't sound like the real thing."

Fan Works

 * At the height of Pottermania were many lame "parodies" that involved... get this!... Harry Potter entering puberty and being a very unpleasant teenager! Who wants to read a book about that? Apparently they were expecting the later entries to continue the "kid in a candy store" sense of wonder from the first book instead of maturing along with the target audience.
 * When Emma Watson appeared on The Wayne Brady Show to promote the second film, Brady asked Watson if they were making the films quickly, saying "you can't have" it be "Hello, I'm Harry Potter and this is my chamber of puberty."
 * Surprisingly, this is pretty much the only thing the terrible Grim Adventures of Billy and Mandy parodies got right. In the second episode, their Harry Potter stand-in has become a teen... but the joke is that Billy and Mandy (who are standard Western Animation children who never grow up except as a Plot-Relevant Age-Up for a Flash Forward) are bewildered by the concept of aging.
 * There are often Naruto parodies where other, better ninjas will mock Naruto for all of his negative traits, such as his lack of stealth, annoying attitude, and small movepool. Name a single Naruto character that DOESN'T do one of these and they're from Shippuden.

Film
"Sizing up Terri's wardrobe and her smile, she tells her: "You're like some kind of retro Brady Buncher." I hate it when a movie contains its own review."
 * Epic Movie decided to parody X-Men by having Wolverine bend his claws to look like he was flipping the bird, even though this same joke was used at one point in the original movie.
 * Disaster Movie has a kid using foul language toward Hancock, at which point Hancock slaps him. Not exactly an amusing gag to begin with, but particularly not amusing since something even more hilarious actually happens to such a kid in the real movie. Even worse, this actually appeared in some of the trailers.
 * Seltzer and Friedberg continue this in Vampires Suck. The trailer contains a joke where the Jacob ripoff character says his contract states he must be shirtless every 10 minutes. This might be amusing until you consider that his constant shirtlessness was already lampshaded the Twilight movies already.
 * Acknowledged in a way, by Roger Ebert in his review of Raise Your Voice:

Gamebooks

 * Spot's Third First Christmas, according to author Kibo, was "a parody of those crappy 'Choose Your Adventure' books" with many bad endings and only one happy ending which is unreachable from any path. One actual book in the CYOA series, "Inside UFO 54-40," the best ending was deliberately unreachable (and not unreachable by oversight, as it was in plenty of others).

Literature
"Gabriel Utterson:"If he be Mr. Hyde, I shall be Mr. Seek.""
 * We've all heard the Incredibly Lame Pun about playing "Mr. Hyde and Mr. Seek" or "Mr. Hyde-And-Seek", right? That joke, in fact, was made in the original book.

Live Action TV

 * One of the very last Bob Hope specials on NBC tried to lampoon the 1989 Batman movie, and had Hope done up as Jack Nicholson's Joker. Both Batman and Superman were in the skit, and Hope refers to them by derisive names like "Bat-Brain" and "Super-Stupe", and getting laughs from his equally aging studio audience. Hope and his writers must have thought that villains do not talk like that to heroes, but especially since Denny O'Neil, this is almost exactly the way the Joker talks down to opponents.
 * In 1995 Saturday Night Live did a Cirque Du Soleil spoof -- Alegria was in New York at the time -- in which the highlight was a male performer presenting a female performer a bottle of wine, which was treated by the emcee as an amazing and whimsical feat. The skit suffers if you've seen the non-touring Las Vegas production Mystere (which opened in 1993), in which a clown presents a woman with champagne as part of an elaborate comic setpiece.
 * The Chronicle was a Sci Fi Channel TV show that attempted to parody the tabloids, by stating that everything in them was true. The first episode parodied (or ripped off) the plot of the first Men in Black film. Thing is, Men In Black was already a parody/comedy, so there was very little that could be made fun of -- and it had already used the joke of the tabloids being true.
 * Andrea Martin of SCTV once remarked that the only show they couldn't satirize was Laverne and Shirley, because they couldn't come up with any situation that was more ridiculous than what the show already did.
 * In the Mystery Science Theater 3000 episode guide, the writers admit that Catalina Capers was one of the hardest episodes to write, being an unfunny musical comedy, thus making it difficult to effectively mock.

Music

 * There's a parody out there of "The Blue Tail Fly" in which the chorus is changed to "Jimmy drinks corn, and I don't care", meaning that Jimmy is drinking corn whiskey. Apparently the would-be parodists were unaware that the most common interpretation of the lyric "Jimmy crack corn and I don't care" is that of "cracking corn", which is to say, making corn whiskey. They not only failed to parody it, they arguably watered it down a notch...
 * Lady Gaga' is often said to be parodying the pop-music genre by making her performances and appearance increasingly over-the-top and controversial to the point of being ridiculous. In other words, she's parodying pop stars by doing the same thing they've all been doing for decades.

Newspaper Comics

 * Mother Goose and Grimm:
 * There was a comic once of a man watching TV with a woman behind him looking shocked, and the caption, "Scully discovers the XXX Files." Which wasn't actually funny if you had any knowledge of The X-Files, since it was well-established that Mulder really did stash porn all over the office, and that Scully was perfectly aware of it and didn't care. (Not that it would be all that funny anyway...)
 * Another strip featured Edward Scissorhands playing Rock, Paper, Scissors with a little kid, and continually losing. This joke especially falls flat considering it was used in the movie as a running gag. And he did it again.

Radio

 * The Bob and Tom Show likes to cast its hosts and/or characters in wacky variants on recent hit movies, and fell victim to this when they cast white trash caricature Donnie Baker in "Funeral Crashers" -- apparently unaware that the concept of picking up women at a funeral had already been explored in the third act of Wedding Crashers.

Theater

 * Lampshaded/parodied by Forbidden Broadway's take on "The Song That Goes Like This" from Spamalot. The song starts out using the exact same lyrics as the original, then points out that fact, and then accuses the show of stealing from Forbidden Broadway.

Web Comics

 * This Bob the Angry Flower parody sequel to Atlas Shrugged has been widely circulated where people admit, sometimes quite proudly, that they found Ayn Rand's book too long to read. If they had actually read it through, they might have discovered that industrialists such as Dwight Sanders do take up farming after leaving the world behind for Galt's Gulch.

Web Original

 * Avatar the Abridged Series suffers from this some of the time, due to parodying a show that already has a high joke quotient. For example, its parody of the episode "The Storm" has a scene where Katara says: "Aang would never run away! [Aang gets on his glider and flies off] Aang, stop running away!" The original was exactly the same, only with different wording.
 * Before he became The Irate Gamer, Chris Bores made a "parody" of Myth Busters. Though it's not as much a parody as it is a bland imitation.
 * Key of Awesome's "I Need A Doctor" parody pokes fun at the Ho Yay between Dr Dre and Eminem by having Eminem hit blatantly on Dre, Dre responding with a sarcastic and only mildly irritated rejection, and Eminem desperately attempting to backpedal and pretend he didn't mean it to regain some shred of heterosexuality. Eminem used this exact same joke in the song and video "Lose It", where he hits on Dre at a bar, and when he gets shot down, claims he's blind. The song and video also had a Ho Yay-ridden hook that went "Yeah, boy, shake that thing - whoops, I mean girl. Girl girl girl" and a section where Eminem cosplayed gay icon Madonna.
 * In The Nostalgia Critic's review of Casper, he ends by making a lengthy Ghostbusters joke, despite the fact that such a joke was already made in the movie and he showed it. In his Top 11 Drug PSA's, he makes a joke about a Star Wars smoking one about robots not having lungs to damage...which C-3PO himself comments in the PSA.
 * An online video called The Hungry Games, mocking the trailer for The Hunger Games in making it about an eating contest, calls the main character "Catnip" as a Parody Name. The creator evidently didn't realize that in-universe, that's Gale's personal nickname for Katniss.
 * College Humor made a fake trailer for a version of The Dark Knight done in the style of the 1960s Batman TV show. Much of the humor seems to rely on the apparent fact that a movie about this incarnation of Batman would turn out way too silly. Someone must not have gotten word that this TV show does have a very silly movie.

Western Animation

 * Robot Chicken and The TV Land Awards have both featured skits that combine Sex and The City with The Golden Girls, or at least were aimed in that direction. Problem is, 70% of the humor in The Golden Girls derives from these aging women unashamedly talking about their sex lives.
 * The array of Marvel-esque superheroes in the supporting cast of Dexters Laboratory includes, among others, Major Glory, Valhallan, The Infraggable Krunk, Living Bullet, Miss Spell, and... White Tiger, who, while a Black Panther parody, shares a name with a real Marvel character.