Attack on Titan sounds like an assault on the largest moon of Saturn. The series could be more accurately named as Attack of the Titans. Its Japanese name, Shingeki no Kyojin, literally means "Advancing Giants", which is a much more indicative and fitting title. It turns out that the Japanese title is the official name of the Rogue Titan.
Osaka: Okay, so, you know how we write "dolphins" as "sea pig"? Sakaki: Uh-huh. Osaka: But we use the same character for "pig" in "river pig" and somehow it comes out as "puffer fish", but they live in the sea.
Osaka herself is an example; she doesn't really fit the Osakan stereotype, and isn't even originally from Osaka, but Tomo decided to give her the nickname, and it stuck.
Starrk has the theme and appearance of a cowboy gunslinger. Despite his name being Coyote Starrk, his Animal Motif is the wolf. His background is that of a lone wolf who desperately wants to be part of the pack and his power, Los Lobos ("The Wolves"), allows him to split his souls into both companions and an entire pack of soul wolf weapons.
"Gerifalte" is Spanish for "gyrfalcon" but Patros's true form barely looks like one.
Jabalì supposedly means "boar". Aldegor's anything but boar-like.
Daily Life with Monster Girl has Doppel, an Eldritch Abomination masquerading as a Cute Monster Girl. Her nickname (her actual name cannot be pronounced or understood by humans) implies she's a doppelgänger, but she's actually a shapeshifter. Doppelgänger are exact copies or look-alikes of a single person, while Doppel can turn into anyone, and possibly anything.
The killer bee species is actually closer to hornets.
There is a species called "Flymon" even though they're really closer to bees. In fairness, they do, in fact, fly.
A Dub Name Change inflicts this on Anomalocarimon, renaming him into Scorpiomon despite the fact that he looks nothing like a scorpion beside the tail and clearly being based on some variety of prehistoric crustacean.
Android 17, Android 18 & Android 20 are actually Cyborgs. This one is because the Japanese name for all the "Androids" translates into English as the rather generic "artificial human", which covers actual robots such as Androids 8 and 19 as well as humans turned cyborgs like the aforementioned 17, 18 and 20; about the only way in Japanese to unambiguously distinguish between androids and cyborgs without resorting to neologism is to use loanwords (i.e. andoroido and saiboogu).
The universe is generally well-populated with very powerful villains whose names don't sound particularly threatening, particularly with a tendency to be named after objects. Piccolo, Freeza, Cooler, Cell, Baby, Garlic Jr. - if you got on the wrong side of any of these people, they could destroy everything you know and love. In most cases, up to and including your whole planet.
Gohan at the time of the Cell Games is usually referred to as "Teen Gohan", despite having been eleven at the time. This is mostly for the sake of distinguishing him from his prior appearances (Kid Gohan, when he was 5-10 years old) and his later appearances (Adult Gohan, when he was in his mid-late teens or adulthood). Presumably, "Adolescent Gohan" was too wordy.
The Snipers in EL, who don't ever appear to do any actual sniping in the OVAs, and in fact mostly just use pistols while running around and doing ordinary police work. Though it's possible that The Serial Rapists, while more accurate, wouldn't have gone over as well with the public.
Archer... is not an archer. He has a bow that he can use, but he's primarily a swordsman. The same goes for Gilgamesh, the Archer from the previous Holy Grail War. Word of God has stated either could have gotten the title of Saber (in each Holy Grail War, there's the same set of seven titles the servants go by), but the Saber who is King Arthur fits it even better, and since they often used their swords as range weapons "Archer" was the next best fit. FSN Archer's personal combat philosophies are also quite close to the ideal of Kyūdō. Not to mention the attitude which inspired the Independent Action ability associated with the Archer class being a strong element of characterization in both of the above.
Assassin from the same series is not an assassin. He is a Samurai and he never use any dirty trick. Assassin is really a honorable and honest man who prefers one-to-one battles. There is a reason why a Servant named True Assassin appears in the Heaven's Feel route.
The loose definitions on Servant classes gets Lampshaded in Fate/Grand Order when Arjuna appears with amnesia and (correctly) guesses he's an Archer because he's carrying a bow, and Mash replies that that's not really a guarantee of anything.
Alphonse is indeed an alchemist who is fully made of metal, but the title is in reference to his brother Edward, who has only one automail arm and leg. This is lampshaded early on when people assume Alphonse is the Fullmetal Alchemist.
Less apparent in English, but the Japanese term for alchemy in Fullmetal Alchemist literally means "the art of gold transmutation", which is (almost) never done throughout the series, due to it being illegal to prevent economic chaos.
For those still wondering about it, The Other Wiki has an article on goldfish and most of them are effectively not golden.
The bit about blue lights is a reference to the Japanese language. The lowest light's color is often called "ao", which is an old Japanese word that refers to any color from blue to green. They now have specific terms for blue ("ao") and green ("midori") and a lot of shades in between, but "ao" still can be a number of colors. In this case, she's complaining about using the word "ao" when "midori" would be more accurate.
JoJo's Bizarre Adventure has most characters and their abilities being named after musicians, bands, songs, tarot cards, fashion designers, and Egyptian gods. About a third have names that are relevant to their personalities or powers, another quarter could probably be Fan Wanked, and the rest are pretty much at random. Walking punchlineVanilla Ice lends his name to a brutal vampiric Hero Killer with Portal Cut abilities. In fact, some seem to be reversed, including the heat-controlling villain AC/DC and the electrically-powered Red Hot Chilli Pepper, or the Lightning Bruiser insect Tower of Grey and the cursed radio mast Superfly.
For a series called Kill la Kill, there is very little killing happening. There is a lot of murderous intent and a truckload of violence, but after a student is offed in the first episode's Cold Open, no more onscreen deaths occur until the next-to-last episode. The title is mainly Gratuitous English for the sake of a pun—in Japanese it can be read as something like "cut the clothing" which hints at the fact that the "Life Fibers" in Senketsu and other superpower-granting uniforms are evil alien lifeforms.
Another example is Signum's Sturmfalken which is German for "Storm Falcons." It's ranged attack from a bow which explodes upon contact with the enemy. It doesn't have any relation to storms or winds and the magical arrow doesn't even transform into a bird (it does in the remake movie, though).
Magical Girl Lyrical Nanoha ViVid gives us Vivio Takamachi's device Sacred Heart, a plush bunny without any heart-shaped markings and is not a holy item. This, however, is justified as she named the device after Nanoha's Raising Heart, and Vivio herself is a CloneCrystal Dragon Jesus. There is also Miura Rinaldi, a mage who was trained by the Wolkenritter, and her Sword Draw techniques, which do not involve swords or rapidly taking out any form of weapon. She executes them using her legswhich has magical blades.
The Villain Protagonist from Maou no Hajimekata, commonly just referred to as Aur, has Ain Soph Aur as his actual name, a term coming straight out of the Kabbalah, meaning “The Limitless Light”, a term used to describe God Himself in those teachings; an extremely ironic name considering Aur is a Sorcerer who has declared himself Demon Lord, who engages in many nefarious actions against humanity, not the mention how handles women who were against him at first, that is manipulate them through rape and hypnotism.
Naruto: A rather blatant example: Kabutowari is a hammer and axe linked by a cable. It's referred to as the "bluntsword" and counts as one of the Seven Swords of the Ninja Swordsmen of the Mist.
Pirate crews in One Piece are often named after their captains, but more confusingly, sometimes named after a characteristic of the captain that not everyone in the crew shares. The main characters, the Straw Hat Pirates, are an example, as only Luffy, its captain, frequently wears a straw hat. Another example would be the Red-Haired Pirates, named after the captain's red hair (not everyone in the crew is a redhead). There are also pirate captains whose names are also normal words that can lead to incorrect assumptions about the crews, such as the Kid Pirates (not actually children, but run by Eustass Kid) and the Buggy Pirates (no relation to glitchiness or automobiles, but has Buggy the Clown as its leader).
The literal translation of "Mugiwara Kaizoku" (what Luffy's crew is called in Japanese) is "Straw Pirates", which is also this, as none of them are made of straw, or even strawmen in the metaphorical sense.
Even a couple of the Straw Hats have these as Artifact Titles. Roronoa Zoro is called the "Pirate Hunter", even though he is a pirate himself, because this is what he was known as back when he was still a bounty hunter, and apparently no one ever changed the nickname. Similarly, "The Devil Child" Nico Robin earned the nickname 22 years before the current storyline when she was an 8-year-old child, but this is still her moniker in the present day, even though she's now a 30-year-old woman.
This is also a case of Lost in Translation; despite his title, Whitebeard only has a white mustache and no beard. This is because in Japanese, his title is Shirohige, where hige refers to all kinds of facial hair, beards and mustaches both. Then again, Whitebeard sounds cooler than Whitemustache.
Crocodile is not a crocodile and has nothing to do with crocodiles (though he does keep a banana-gator as a pet). He's a human with the ability to turn into and manipulate sand.
Usopp's hometown, Syrup Village, has nothing to do with syrup.
The Pokémon episode "Haunter vs. Kadabra" does not feature a fight between Haunter and Kadabra. Since Haunter is never owned by Satoshi/Ash, everytime he tries to send it in battle, it disappears. In the end, Pikachu battles Kadabra, then outside of the battlefield, Haunter reappears and makes Natsume/Sabrina laugh so hard, her Kadabra who is spiritually linked to her is unable to battle because it is rolling on the floor laughing.
Princess Principal has two possible interpretations, neither of which is correct. It is not about a princess who is the principal of a school (though she does go to a school). Nor is it about a princess and her bodyguard—"principal" being a term for the person the guard is assigned to protect. Although Ange acts somewhat as a self-appointed bodyguard for the princess, the higher-ups try to make her kill the princess at one point. The intended meaning is that it centers on the agency's "principal team" of spies (why they are called principal is unclear; it's implied they're not particularly high-ranking), which includes a princess. It's nearly a Word Salad Title.
Robot × Laserbeam is actually a golf manga about a teenager nicknamed "Robot" by his classmates for being The Stoic and his signature swing, which sends the golf ball on such a straight path that onlookers call it "The Laserbeam." Aside from the guy's machinelike precision, it is completely mundane in its setting—there are no science fiction or fantasy elements whatsoever.
Tuxedo Mask of Sailor Moon technically does not actually wear a tuxedo; he wears white tie and tails, which is more formal. By definition, a tuxedo (or "dinner suit") has a black bow tie and a suit-style jacket rather than a tailcoat. And either way, it's not a mask.note ("Tuxedo Mask" is a straight translation of "Tuxedo Kamen", owing to a long history of super-hero types with "blank"-kamen names. For the purposes of this series however, he is wearing a "tuxedo" and a "kamen/mask".
Sailor Pluto has an attack called "Dead Scream." While she does represent the planet named after the mythological King of the Dead, she initiates her attack by saying the phrase in a normal to low-volume voice.
Similarly, Sailor Saturn has an attack called "Silence Wall." She does bear the title of "Soldier of Silence" and her weapon is called the "Silence Glaive", but she initiates her attack by screaming the phrase.
School Rumble is described by FUNimation as "The absolute funniest show you'll ever see that's not about anything that rumbles... ever!", although admittedly there is at least a school...
Justin Law of Soul Eater has an attack named "Law Abiding Silver Gun", which is not a gun but a guillotine blade . The name makes no sense except as a Shout-Out to B.Ichi, which had a weapon of the same which was a gun.
Teekyuu! focuses on a tennis club (teekyuu meaning "tennis") that does everything except actually play tennis. At least one character lampshades this.
The weapon names in Tokyo Mew Mew are usually at least straightforward puns, but the Mew Berry Rod is too small to be a rod and not intended to be used by Mew Berry. And what's the "tone" in Mew Mint's Mintonarrow supposed to mean?
And the StrawBellBell (or whatever) didn't even have a bell originally.
Transformers Armada: The Star Sabre has nothing to do with stars. The Skyboom Shield neither flies nor goes 'boom'. The Requiem Blaster is very loud when fired. Who named these things?
Some characters are named for features that later incarnations won't have. Armada Smokescreen doesn't have smoke (though he did once activate such a feature in the Autobots' base... something anyone could've done.) Energon Sixshot doesn't have anything to do with the number six (the original Sixshot had six forms, though the 'shot' is still a misnomer.) Cybertron Crosswise's name has nothing to do with him, though he is a 'monster hunter' and some monsters don't like crosses... but that's really stretching it. The first use of the name was with a guy in Transformers: Robots in Disguise who had a big X on his car hood. G1 Ramjet? An F-15, which doesn't use a ramjet. The list goes on and on.
For those not familiar with Yatterman, you see that girl on the left in this image◊? Her name isn't Yatterwoman, nor is it Yattergirl. She's known as Yatterman-2. It could be reasoned that the "man" in this case is short for "human", but it's still somewhat confusing.
This is an issue that dates back to at least Science Ninja Team Gatchaman, another superhero team whose name ends in "man" but includes a woman.
Team 5D's is named after the five Signer Dragons, but has seven members. It does not help that there are six Signer Dragons (although it were originally five prior to Executive Meddling).
Jack's Evil Knockoff has three copies of Red Daemon's Dragon. However, none of them are red like the original.
Yu-Gi-Oh! itself. The title means "King of Games", and refers to Yami no Yugi/Atem, who goes back to his own time at the end of the first series and hasn't been seen since, yet the series is still called King of Games even though the King of Games isn't in it anymore.
The third segment of Robotech (based on Genesis Climber MOSPEADA) is also called Robotech: The New Generation. However, technically, the new generation actually started with the The Southern Cross Robotech Masters'; General Leonard's opening monologue explicitly stated how the defense of the Earth was now in the hands of a new generation. The name may have been saved for the third segment due to the focus on how the younger members of the returning expeditionary force had few memories of Earth, but had they been born on Earth, they would have been roughly of the same generation (minus a few years) that fought the Masters.