The Eccentric Family'scover◊ makes you think that the girl next to Yasaburo is the female lead but she is actually one of Yasaburo's forms and Benten—the purple-haired one, barely visible behind the pot-bellied tanuki statue—is the actual female lead.
The far-out extreme would be the cover of Warriors of the Wind, the original dub of the classic anime film Nausicaä of the Valley of the Wind done in the mid-'80s. The artist just made things up and added characters and elements◊ that weren't in the movie at allnote There were no flying horses, guns, robots, swords made of light, or shadow-men, the monsters in the movie the one on the cover vaguely resembled were not ever ridden, and of those five characters only the one on the right looks anything like a character in the actual movie (Nausicaa, who even then wasn't blonde).. The dub itself wasn't an accurate representation of Hayao Miyazaki's work either, but it wasn't that different.
Some of the DVD covers for End of Evangelion have Toji featured in his pilot gear. Not only does Toji not appear in the film at all, but he'd already been crippled by that point in the story anyway.
Mazinkaiser had an episode titled "Kouji Kabuto Dies in Lava!". No points for guessing what happens (or rather, doesn't happen).
On the very last DiC English dub DVD of Sailor Moon R, "Love Conquers All", Sailor Chibi Moon is pictured alongside Neo-Queen Serenity. However, Chibiusa doesn't actually show up as a Sailor Senshi until halfway through the next season. Apart from being spoileriffic, entirely different companies did those seasons. DiC did Classic and R, while S and SuperS were done by Cloverway (Sailor Stars wasn't dubbed until Viz Media gained the rights).
Almost ALL of the Sailor Moon bootleg covers feature pictures from the wrong season.
The cover of the fourth DVD◊ Black Lagoon DVDs depicts Hansel and Gretel as a pair of cheerful smiling gothic lolis. Anyone who's actually seen the episodes concerning them will know they are probably the most horrific examples of fearsomeness that exist in any anime that doesn't involve the supernatural. And probably some that do.
Possibly the example with the biggest chance of emotional scarring: Narutaru. The back cover of the first English volume describes it as "A rare mix of breathtaking fantasy and gripping action/adventure, filled with imagination, excitement, and delight." Paired with the way everything on the cover depicts the main character happily flying around against a pink background, and you've got a good cover to attract little girls looking for a magical girl series. Except for the fact that Narutaru is actually seinen, and extremely disturbing seinen at that. Whoops. (That aforementioned blurb also proves that Dark Horse really hadn't done their research when they first got hold of the manga...) The opening of the anime is even worse; not only does it have a super-cute art style and a very upbeat theme song, but it references some shocking events from later in the series and treats them like a joke. Also, one of the DVD covers features one of the side characters, Hiroko, smiling like a typical Cheerful Child. Let's just say she's not quite like that in canon.
The box sets and covers feature characters wearing skimpy clothing they don't wear in the series (and an odd emphasis on implied twincest, which, while refuted by canon on both sides, is often used for fanservice in promo pictures) for the first season. The second season's box art is still full of cuteness, often with Rika and Satoko. This, too, is only an accurate representation of about 40% of the series's content. The other 60% is murder.
The OVAs are even worse; they're full of the girls wearing very little clothing. Even Hanyuu and Rika, two girls who appear to be about nine years old.
The English DVD covers are in negative, giving them a creepy look, despite the fact that the art is happy and cute. It's a thematic reflection of what happens when you don't trust your True Companions. You can, however, turn it inside out to get the normal look, and the Japanese boxset covers are posters you find inside the box.
The manga, at least, averts the trope - the covers are the characters in their normal attire, surrounded by blood splatters.
The first boxset of Princess Tutu in America drew a lot of fire for choosing to put Rue on the cover in a skimpy outfit instead of the main Magical Girl herself. ADV Films likely got a lot of complaints, because later editions switched to a cover with Tutu as the focus.
Neo Ranga's cover depicts the trio of sisters who compose the main characters wielding huge wicked looking swords and wearing nothing but body paint. In reality the series is more of a giant robot-style deal, and while the characters do don the body paint at one point during the series (albeit with clothes), the giant swords are completely absent.
The covers of Fruits Basket, due to the system used to decide who's on the cover (more or less appearance order at least at the start), the character on the cover often doesn't appear much or even at all inside the book. The final two books feature Tohru's father and mother, both of whom are deceased. This is lampshaded in several cases, when filler pictures of the characters complain about how little they are in the story.
The front cover◊ of the North American DVD release for Simoun featured Neveril and Aeru sort of...hugging? Dancing? Playing patty-cake? Whatever they are doing they are close together and naked, but somehow their embrace has no sexual overtones at all, so the whole thing just looks weird. Also, there is not a single Simoun visible on the front cover, back cover, or spine. The series is namedSimoun and the machines are nowhere to be found. Without already knowing the background to the series there is no way to determine even what genre the show is, first guess would probably go to Magical Girl or an Ecchi series.
Many covers and promotional artworks of Magical Girl Lyrical Nanoha Vi Vid feature Einhard together with Fate, even though they rarely interact with each other. It's mostly symbolic, since Einhard is basically Vivio's version of Fate.
Many special editions feature characters that don't have much prominence in the story or random fanservice scenes or something completely different that don't happen there at all.
Each volume of the true colored edition features a character who doesn't have much prominence, except Lily and possibly Hayate.
This trope could be applied to the Dragon Ball GT season sets. The first set, containing the first 34 episodes, features Super Saiyan 4 Goku on the cover, Super Saiyan 4 being a form Goku first achieves in episode 35. And the second set features Super Saiyan 4 Gogeta, a One Episode Wonder from late in the series.
When the Saban-dubbed episodes of Dragon Ball Z were released on DVD by Pioneer, there were three covers for the Namek arc that shown concept art of the characters past the Saban run. The concept art in question? Vegeta in the outfit he wore during the Freeza fight, Goku preparing the Spirit Bomb to use against Freeza and Goku as a Super Saiyan with the last one being on two of the three covers. Kid Goku is on the last cover, but he's not shown in any flashbacks in the episodes on that set.
Would you think Bleach would be about fighting ghost with samurai swords with a cover like this?◊
An even better example is the cover of Volume 34, which has Adult Nel on the cover◊. If you were a newcomer to Bleach you could be forgiven for thinking that adult Nel would play a significant role in this volume. In actuality, she has a total of 7 pages worth of screentime (that's counting a Double-Page spread as 2 Pages) and everything from her transformation into her adult form to her backstory was in Volume 33.
In a combination of this and "What do you mean, it's not for kids?", the most sexually explicit yaoi manga are often mistaken for tamer series due to the heavy use of pastel-tones and flowers.
The manga prequel to Hellgate: London has a cover that looks like a nice Dragon Ball-esque adventure, with the main characters and their family arranged in a happy little formation. The actual content is far from what this implies-most of the family is brutally slaughtered near the end, and that's not even getting into what comes before that.
The US cover art for Initial D Third Stage shows a car that appears for all of 5 minutes of the movie, and the race against said car, despite being on Battle Stage, isn't much of one.
At last one edition of the first book of Barefoot Gen suffers from it. The story is far less happy than its cover◊. What a happy looking series... about the atomic bombing of Hiroshima.
Might be true for a Japanese audience. However, given pretty much the only thing Hiroshima is known for to people outside Japan, anyone who can't guess what "A cartoon story of Hiroshima" is going to wind up being about fails history forever.
The Ace Attorney "Official Casebook" manga collections have back cover blurbs that make it sound like the stories involved in the books will all involve mystery solving and legal action in the vein of the games. Though there are a few mysteries involved most of the stories are just Slice of Life pieces about the characters outside of court.
Many volumes of Rave Master have highly nonsensical/comical cover art which has absolutely nothing to do with the volume's story. One of the weirdest ones involved Haru and friends snowboarding.
The cover of the first volume of the North American release of Sukisho have the title characters holding each other, surrounded by multitudes of bright pink flowers. Seems perfectly innocent, right? Or at least it does until you know what it'sabout.
One Piece Volume 59 has Ace looking ready to kick some ass, even though he's mortally injured at the start of the volume and dead at the end of the first chapter.
It could simply be as a tribute to the character, since this is the last time he appears.
The first volume has Nami on the cover, sitting in a boat with Luffy and Zoro. She only appears near the end, and joins the crew in the second volume.
The Spin-Off manga Puella Magi Oriko Magica has a variation. Almost everyone assumed that the green haired girl on the cover of the first volume was the eponymous Oriko. Then the official preview images were released, revealing that she wasn't Oriko.
The cutesy cover of Volume 2◊ (not used for the U.S. release) does this sneakily. It is, in fact, an accurate portrayal of the literally candy-filled setting and upbeat mood of a scene in that volume... except, ten seconds later, things get ugly. Specifically, the girl on the left is gruesomely decapitated. Though it almost doesn't matter, since this scene is approaching It Was His Sled territory in the anime fandom.
Not helped by all by its merchandise even post-The Reveal playing up the Moe factor.
Some English Azumanga Daioh DVDs show the girls with their stomachs exposed, blushing, and their skirts looking like they're going to fly up; Yomi is not only blushing, but is covering her skirt, making the series look like a fanservice anime. Subverted, as they were actually from the first 4 seconds of the opening.
Wandering Son covers show the two Transsexual characters 'cross-dressing', when in the series they rarely dress up like that (especially the protagonist). The coloring of the characters is often incorrect, retcons and Art Evolution aside. The back of the first volume shows Maho with blond hair while the inner artwork at the beginning of the manga shows her her normal brown.
In the Warrior Cats manga Escape From The Forest, Tigerstar gets the cover all to himself, implying that he will be important in it, however he only appears once to ask the protagonist a question. After she answers it, he is not seen again.
Miracle Girls covers almost always have the characters with incorrect haircolors. The mangaka lampshades this in her omakes, saying that it's due to the printing process and her original images had the correct colors.
The cover of the Burst Angel OVA makes it look like a sequel to the TV series. It's actually a PREQUEL, set between a flashback episode and the rest of the series.
A handful of early DVD covers for the Hungarian release of Transformers Armada show off characters that either haven't been introduced yet in the episodes that are on the disc, or use colorations that the characters only take on way-way later.
The cover of Divergence Eve looks like a generic mecha series with lots of fanservice - when really the breasts of the lead characters are the last thing you end up thinking about whilst watching the show... and its incredibly complicated plot.
Early promotional material for Digimon Tamers portrayed Impmon in typical Big Bad fashion, as he was at the time planned as the series's main antagonist. This route was later abandoned.
Where to begin with the "Digimon: The Movie" poster/DVD & VHS art? The posters show the original Season 1 characters as depicted in Season 2 (high-school age), but these characters are mostly shown at their Season 1 ages (and all but Tai, Izzy, Matt and Sora have glorified cameos). Davis, Yolei and Cody are depicted in their Digi World outfits—they never wear them during the movie and never enter the Digi World. Terriermon (who haves 3 horns on his forehead rather than only one - basically, is actually a recolored Lopmon) is shown along with what is possibly supposed to be Kokomon's rookie form, Lopmon—only Lopmon never appears in the movie and is shown inaccurately on the cover as a demented, fanged Terriermon. Oh, and the back of the VHS and DVD case features a plot summary about the older kids being kidnapped by a rogue Digimon—a plotline completely cut out of the dubbed movie.
Purposely done with the Japanese version of Sayonara, Zetsubou-Sensei as the bookflap blurb describes nonsensical stories that had nothing to do with the actual contents.
The cover art of one American Haruhi Suzumiya DVD release shows Haruhi standing alone with her shadow being that of her Bunny Girl outfit, implying that a bunny girl plays a much larger role in the plot than it actually does.
One of two different DVD covers used by Central Park Media for the OVA Strange Love (AKA Hen) depicted two characters kissing, in front of an abstract red/pink background. One of them is the main character (Chizuru), but the black-haired girl is a very minor character with little screentime and is not Chizuru's love interest — the picture was taken from an Imagine Spot scene that explains that Chizuru isn't attracted to her or any other women, with one exception.
The VHS cover art for The Enchanted Journey features Glicko and Nono as giant anthropomorphic chipmunks walking on their hind legs, carrying backpacks, and having human like hands; in the film however neither are anthropomorphic in any way.
The Parkfield Playtime release of Codename: Robotech in the UK. As well as the terrible day-glo cover art which doesn't match the original art style at all and is obviously meant to scream "we are marketing this for kids", but the character on the front doesn't even appear in the feature: it's the adult Dana Sterling from The Masters segment note a.k.a. Jeanne Franciax from Super Dimension Cavalry Southern Cross, when the feature covers The Macross Saga only and doesn't even get to the point where baby Dana is born! Mercilessly parodied in this online review.
Though it would seem she does appear briefly, in the pose depicted, in the original Robotech intro.
The VHS cover for the "My Favorite Fairy Tales presents The Three Little Pigs" the pigs look like a mixture between the Disney animated versions and the claymation versions featured in the Green Jelly music video. In the actual animation they look nothing like that: they're small with round heads and bodies and big eyes in a stylized anime style, and the wolf on the back of the cover only vaguely resembles how he looks in the video.
The VHS for "Little Red Riding Hood" depicts her looking like a blonde Pippi Longstocking with pigtails and freckles and the wolf looks very Chuck Jones inspired wearing overalls and a top hat, in the actual animation Red is small with curly blonde hair and big blue eyes while the wolf looks identical to the one from "The Three Little Pigs" and wears only a vest and pants.
The poster for the English language release of the 1977 Space Battleship Yamato (Called Space Cruiser at the time) film has the Wave Motion Gun being used as a launch tube for a spaceship. The spaceship isn't even one that Yamato carries but the alien Iscandarian ship that carries the message from Queen Starsha. Also, Analyzer is now a mass produced robot as there are three of him seen in this poster.
From the artwork for the first Blu-ray edition of Ranma ˝, you'd think Akane was a skilled martial rhythmic gymnast. However, she only does it for an episode and a half, is shown to be very horrible at it (though she does show some improvement a bit later on), and is incapacitated by a foot injury before she can even compete. Plus, her leotard isn't pink.
The DVD/Blu-ray cover◊ of the Maiden Japan edition of Patlabor: The New Files, sharing cover art with an original Japanese release of an episode, is a temporal anomaly, as it portrays Noa Izumi as both an adult and a child. Child!Izumi is holding Alphonse the dog, who died during her time.
MJ's cover◊ to their 4th volume of the Patlabor TV series features Kanuka Clancy, who had left the series by that point and only appears on the set in a dream sequence. Richard Wong, the other character featured on the cover, isn't there either as the Griffin arc had stopped (to be continued in The New Files OVA) by that point.
Attack on Titan: The cover of the 9th volume shows Eren and Mikasa facing the Beast Titan. The only character directly facing said Titan in the volume is Mike, while Sasha, Connie, Ymir, Reiner and Bertolt witnesses him from a distance. Eren and Mikasa are nowhere at the scene.
In the Volume 6 cover of Fairy Tail, Levy is slightly more busty than she should be... Though to be fair, it's also a question of Art Evolution. The page caption is from the start of the series, where she was actually drawn having breasts, just quite smaller than the ones she got in the caption. Nowadays, she is the series' resident Pettanko, not counting Wendy who is simply too young to have grown breasts.
Possibly owing to the popularity of Little Bit Beastly character designs in Japan compared to anthropomorphic ones, Wolf Children Ame and Yuki 's promotional poster and DVD covers feature the titular kids being held by their mother while both are sporting wolf ears and wolf tails, but otherwise human bodies. This is never the case in the film - they're only ever classic werewolf-esque anthropomorphic wolves or quadrupedal ones.
The covers and other official art for School-Live! depict the girls as doing cute things and looking fashionable. The manga is about a series of girls surviving on their own in a Zombie Apocalypse, plus they rarely change clothes. Two of the chapter covers apparently influenced the anime: One features Miki taking a picture of a puppy, which probably explains the relationship between her and Ascended Extra Taroumaru, while a cover of the girls in swimsuits is likely why the random pool episode occurred.
The chapter covers for Yuureitou would make you think Tetsuo is Ms. Fanservice and the series has a lot of fanservice. It's actually a noir mystery-murder and Tetsuo is a trans man who would never flaunt or dress as depicted.
The covers to the rerelease of Stop Hibari Kun feature new artwork done by Eguichi Hisashi. The problem is that his art style changedvastly over the twenty year gap and thus the character designs don't reflect the inside art.
A relatively mild example, but the Right Stuf re-release of the Mobile Suit GundamCompilation Movie trilogy uses one of Yoshikazu Yasuhiko's Mobile Suit Gundam: The Origin illustrations for the cover. Origin Gundam has several minor but notable differences from the original anime version that are prominently visible, such as the hatch of its retractable Shoulder Cannon, red eye lenses as opposed to yellow and even the different model number painted on its chest (RX-78-02 rather than the original's RX-78-2).
Every Detective Conan manga cover features the main protagonist in an outfit you will never see him wear standing in front of a real life photograph of something that is often times unrelated. Example: 
One DVD Croatian release of Thumbelina: A Magical Story by Bambbino takes it to the extreme; the case and DVD art both clearly depict characters from the aforementioned movie (aside from a miscolored red Noble on the back of the case), with the case also featuring the movie's synopsis and length at 85 minutes, but the actual content on the DVD is a whole different story - namely, an entirely separate adaptation by Burbank Animation Studios that lasts less than 45 minutes and has its own DVD case in the Croatian market◊ - where the only thing it has in common with the movie that's being advertised is the title and the story they were both adapted from.