Legendary Catfish

"...and then I saw
that from his lower lip
...hung five old pieces of fish-line,
...A green line, frayed at the end
where he broke it, two heavier lines,
and a fine black thread
still crimped from the strain and snap
when it broke and he got away.
Like medals with their ribbons
frayed and wavering,
a five-haired beard of wisdom
trailing from his aching jaw."

—"The Fish" by Elizabeth Bishop

Those legendary giant fish that inhabit certain lakes. They usually have names like "Bubba" or "Sherman". The exact kind of fish is usually a Catfish. They each have a story on how they're old as the lake itself, big as a bus, and almost impossible to catch.

That almost part is important. The protagonist will thus be encouraged to go out and be The One To Catch The Legendary Catfish. Eventually he does so and he has a huge battle with it. Finally the protagonist wins the fight and the great fish gives in. Inevitably, the protagonist lets the fish go; usually he says that "the legend must live on" or makes up some other excuse.

In a more general sense, an animal that ought to be considered easy prey, yet it is also a vicious creature that attacks you instead, succeeds in biting you and leaving a nasty scar (sometimes despite having no teeth!). Oh, and it's darn near impossible to kill no matter how hard you beat on it, or how many bones you break.

Bonus points if catching it requires the use of your own flesh as live bait.

Note that not all catfish in fiction are Legendary Catfish, and not all examples of Legendary Catfish are literal catfish. But in the places where catfish are common, they are well known for attempting to eat anything they can swallow, grow to enormous size given enough food, drive out other fish, and be extremely difficult to kill.

Truth in Television, at least in Eurasia. Look up the "wels catfish", also called a "sheatfish". They can be up to 10 ft long (3m) and weigh 330 lbs (150 kg). They eat ducks.

Compare Legendary Carp. See "Noodling". Not related to "Catfishing", a term that can apply in a Dating Service Disaster.

Maybe it's a Killer Rabbit, Evil Squirrel, or a Rabid Raccoon, or the actual evil Catfish himself (Several shows will have a whole episode about an evil vicious Catfish), but if it's an animal that should be easy prey, but turns into a Moby Dick-style Animal Nemesis you've sworn to kill or die trying, you're probably dealing with a Legendary Catfish.

Examples of Legendary Catfish include:

Anime and Manga

Gon in Hunter X Hunter is introduced by catching the King of the Lake, a massive fish that dwells in a lake on his island, by using his nature skills.
The Pokémon Whiscash is based on a catfish. Specifically, a mythical Japanese earthquake catfish. There was an episode of the Pokemon anime that used this plot, with an old man trying for years to capture a famous giant Whiscash. Finally he gets a Master Ball to use on the Whiscash and the Whiscash eats it.
Is Voltes V obscure enough for you Western types? It had a Humongous Mecha catfish for its Monster of the Week. And it wasn't just an ordinary Monster of the Week, it was a Monster of the Week that can interrupt the titular Super Robot's Transformation Sequence!

Comic Books

Archie Comics' Little Archie spin-off featured The Perilous Pike, a huge pike that Mister Weatherbee constantly tried (and failed) to capture.
"Let him catch the great king sturgeon! That will prove if he be worthy to be friends to the Peeweegah!"

Film

At the beginning of Big Fish, Edward Bloom tells a story about how, when his son was being born, he was busy being dragged around a lake after having been foolish enough to try to catch one of these legendary catfish. After having used his wedding ring as bait.

Literature

Moby Dick.
The Old Man and the Sea by Ernest Hemingway.
"The Fish" by Elizabeth Bishop, quoted above, is a poem about a boy who catches a fish seemingly old as the sea. Big, googly eyes, huge teeth, hooks from the fishers who failed still in her mouth like lip-piercings and badges of courage, scarred all over with fins worn down to ribbons and - in the narrator's eyes - beautiful in his own way. Like he's survived everything the world can throw at him. And since this legend seriously deserves to live on,

"Everything was rainbow, rainbow, rainbow - and I let the fish go."

- Compare "Pike" by Ted Hughes, pike are one of those fish whose growth is limited by the body of water they live in and the food supply and they can get eat-your-dog big.
There's also a books of New England humor that suggests a name for this kind of Legendary Fish: "Knock Less Monster". As in "Knock (back) Less (alchohol while fishing) Monster".
The Irvin S. Cobb story "Fishhead."
In David Eddings' Polgara the Sorceress, one character is convinced to keep his true identity as the lost prince of Riva a secret by getting him hooked on trying to catch one of the local Catfishes, "Old Twister" - and, should he ever succeed, intends to let Old Twister go again. When Old Twister turns up dead after a hard winter, the heir actually gives up fishing.
In William Faulkner's The Sound and the Fury, there is an eddy outside of Boston inhabited by a trout which has been eluding capture for 25 years. A store in Boston offers a $25 fishing rod to anyone who catches it. The main character, after observing a group of boys looking out at the Eddy and coveting the prize, tells them, "Only don't catch that old fellow down there. He deserves to be let alone." One of the kids remark, "Can't anybody catch that fish."
In A Canticle for Leibowitz, the giant catfish Bo'dollos is rumoured to haunt a lake formed over a crater once occupied by a village and 'an intercontinental launching pad, complete with several fascinating subterranean storage tanks.' Incidentally, the site was excavated by the Venerable Boedullus.
The ultimate example has to be the short story "God's Hooks" by Howard Waldrop.
In The Sword in the Stone (book by T. H. White and Disney movie both) Wart and Merlin encounter the king fish of the moat, who argues that "might is right."
In December Boys, an old fisherman named Shellback spends his days trying to catch a huge fish called Henry, and was visibly upset when one of the orphans beat him in catching Henry.

Live-Action TV

The show River Monsters and variants, are all about this.
- They did a show about giant catfish in Germany, where tradition going back hundreds of years says, they eat people. It turns out they only nip at them a little. Overlaps with Legendary Carp.
  - In the episode focusing on them, he notes that the ones that've been allowed to breed in Barcelona are growing much bigger than the ones from their homeland typically do (thanks to warmer environment, basically), and it shouldn't be more than a few years before there genuinely will be ones big enough in those rivers to drag fishermen off the banks and swallow people whole.
- A specific subspecies of catfish, on the other hand, is definitely Truth in Television. The Goonch catfish of India, given the right environment, can certainly reach man-eating size. It's also notable (not unique, but notable) among catfish in that it's a predator rather than a scavenger. Jeremy Wade caught a five-foot-long one that weighed almost 170 pounds, and it wasn't quite big enough to eat a person—which means that the man-eating fish of the stories is still out there.
In one of the comedy episodes, Xena goes hunting for "Solaris" instead of chasing down the villain of the week thanks to meddling by Aphrodite. She still gets them in the end, of course..and then shoots the fish into the sky, turning it into a constellation for good measure. This would also be the episode where the infamous "she wants me to fist a fish?" line came from.

Music

Boudreaux Was a Nutcase, by The Austin Lounge Lizards. This one's a large-mouthed bass, named Moby Jack.
Cledus T Judd has a song called Goodbye, Squirrel!, which is a parody of the Dixi Chicks' song Goodbye Earl. The song tells the story of a couple of deer hunters who were thwarted from shooting a 34-point buck by a squirrel that jumped out of a tree and onto one of the hunters, causing him to fall out of the tree stand. The hunters return with TNT and M-80 fireworks and proceed to blow up a section of the forest (and themselves) in an attempt to kill the squirrel. The squirrel survived unharmed, but the hunters were "barely alive by the time the game warden arrived".

Newspaper Comics

Khan, the giant catfish, is Julius' nemesis in Liberty Meadows. Julius reacts to sightings of Khan the same way that Captain Ahab reacts to reports of Moby Dick.

Oral Tradition, Folklore, Myths and Legends

The association of catfishes with earthquakes seems rather common in Japanese works. This goes back to a Japanese legend that earthquakes are caused by a giant catfish wriggling in the mud underneath the earth.
This Urban Legend about a giant catfish.
Every Single Lake in America has its own Legendary Fish. Or at least some other awesome Folkie Tale or Legendary Legend, sometimes with cool gory bits. Make sure to ask around every time you visit one.
- OK, OK, every single large, natural lake, and only the ones that don't have prehistoric monsters in them.
Russian folklore features the sentient "Miraculous Whale Fish", whose body was turned into a floating town as a divine punishment for swallowing thirty ships ages ago. The Protagonist tells the Whale Fish about the punishment's reason, after which it spits out all of the ships unharmed together with the crew. As soon as it's free from its curse, it starts helping the protagonist.

Real Life

Arguable example: This Real Life example.
- Even Bigger ones here:
In 2006 there was a rumour that a sea monster had been seen in the moats of Varberg Fortress in Sweden. A woman who was out walking her dog had seen something huge shoot up from the water and swallow a gull in midflight. The monster turned out to be a large catfish.
Reggie: a feral Gator swimming in Machado Lake in Harbor City, California. After over a year, he was caught in May 2007 and currently^[when?] resides in the LA Zoo. The late Steve Irwin would've had a go...if not for his unfortunate accident.
Benson the giant carp, formerly of Bluebell Lakes, England.
- - The Watts bar catfish in TN. I've heard stories that divers will only go down there once or they won't go down without A FRIKKIN CAGE!

Video Games

In Breath of Fire IV, there's a Bonus Boss to be encountered by approaching the hexed city of Chamba from the back (in other words, go to the next waypoint after Chamba and return). This boss is a gigantic Angler fish, called (appropriately enough) "Angler". Beating him earns you the North Chamba fishing spot, which is full of Jellyfish and some of the biggest catfish in the game. If you want to get the highest possible rank for catfish, this is your fishing spot!
There is a cross-dressing talking giant catfish in Dark Cloud 2
In Lufia II: Rise of the Sinistrals, the first actually somewhat challenging enemy happens to be a giant, bored catfish that has been tormenting the nearby village with earthquakes.
Volt Catfish from Mega Man X3.
Okami has you catch these two times in the main story: a giant catfish that ate the reflection of the moon and a "living sword" (i.e., cutlass fish). There's also That One Fish, a nigh-impossible to catch extra-special ingredient that must be caught for One Hundred Percent Completion and to unlock a hidden brush technique. The marlin is truly a beast of pure evil.
Okamiden Has one as well. A giant evil catfish that convinced himself that he was a Carp that would turn into a catfish when he climbed up a waterfall.
In Castle Crashers one of the bosses is, literally, a Catfish. In more ways than one.
The Unnamed Giant Catfish of Touhou Hisoutensoku. Avatar of the God of Natural Catastrophes, and (imaginary) archenemy of Hong "China" Meiling.
Opoona has the aptly named fish "Legend". Though, the point of the battle is only to collect a scale, not to truly catch it.
Endless Ocean and its sequel have several examples, though you only observe them, not catch them. Examples include Magu Tapah and Thanatos, giant great white sharks; the Ancient Mother, a giant whale; and the Golden Catfish.
- The sequel has three stronger examples the Sea Serpent, Anomalocaris, and Cameroceras all of which you can't directly interact with and agree to never speak of again.
In Persona 4, you actually have to catch one to max out a Social Link.
- To the horror of many.
- Once you catch the Guardian, you can use it to fully restore a party member's SP... or feed it to a cat to cut the feedings needed to complete "Cat Needs Food Badly" from twenty to four.
In The Legend of Zelda fishing minigames, there is often a big fish of this sort that will earn you the maximum prize for catching it.
- It's usually the "Hylian loach", and it has a tendency to be utterly impossible to catch, unless you have a special lure that the fishing hole's proprietor may or may not approve of, in which case it's merely nigh-impossible to catch.
The gaint lung fish from Psychonauts.
In Ape Escape, there's a level in the Primordial Era where you have to catch apes in an ancient jungle. Earlier you learn how to swim, but you can't swim in large areas in this level because a giant catfish lives in the water and will attempt to shock you.
The King Fish in the Harvest Moon games
Final Fantasy XV has two such fish. Catching the Murk Grouper (aka Devil of the Cygillan), is described as an "unrealisable dream" as no-one has caught one in living memory. Then, there's the Liege of the Lake, the Noble Arapaima, which has never been caught.
There are five fish meeting this criteria in Stardew Valley, each one found in a different body of water, and only catchable at specific times of year. The toughest of the five is actually called Legend.
- In an later update of the game, there's a quest to catch their successors, though these appear to infinitely respawn.

Web Comics

In the first month or so of Sluggy Freelance, Bun-Bun was the Killer Rabbit version of this trope. Torg and Riff tried everything to get rid of him, from hammers to killer bears to dimensional portals to lawsuits. Eventually they learned to co-exist with their sociopathic pet, though Bun-Bun still inflicts merciless violence on them from time to time.

Western Animation

Chip and Dale serve this purpose for Donald Duck in countless old Disney shorts.
Doug encounters one such giant catfish in his hometown's lake, having heard stories from his neighbor, Mr. Dink, about the huge monstrous fish known as Chester that had swallowed Mr. Dink's wallet. He discovers at the end, after helping Mr. Dink catch him, that the catfish in question is only a couple feet long. Dink elects to let it go and keep the legend going.
Family Guy did it - with Daggermouth. Who is actually animatronic and made as a way for its owner to make money from merchandising.
This was an episode of Hey Arnold! involving such a fish. But Arnold and Gerald ended up letting the fish go in the end.
The Simpsons. Early season episode where Homer and Marge go to a marriage counseling retreat with Reverend Lovejoy, except Homer only goes to catch the legendary catfish "General Sherman" who populates the retreat's lake. He does catch it—only to throw it back in to show Marge that she matters to him much more. Afterwards, the fishing shop owner tells a patron about the man who caught the fish, but describes him as a giant with tree trunks for arms and hair as fiery as the pits of Hell itself.
Ty gets dragged on a fishing trip by his father that includes the obligatory giant catfish in the Grossology episode "Squirm".
An episode of Nightmare Ned subverts the usual plot- Ned and his dad actually succeed in catching the legendary fish, but after a nightmare, Ned lets it go. Then his dad decides they'll try and catch it every year...
Legend told on Angry Beavers of a fish known as "Old Gramps" which was large enough to swallow a Swede. Turns out its his mate who's the large one, and SHE'S big enough to swallow the Beaver Bros.' dam... along with several Swedes.
The fishing episode of Kid vs. Kat features one.
In the animated Pippi Longstocking, the two policemen are always scheming to catch a giant (pink!) fish in a local lake. At the end of the film, it's lashed to the roof of their car.
A swamp-dwelling fisherman in one of the more recent Scooby Doo cartoons was trying to catch a pesky giant Louisiana catfish. It not only kept stealing his bait, but swam up to his houseboat and spat water in his face to taunt him each time it did so.