"Mugen" is Japanese for "infinity". M.U.G.E.N, however, is a freeware 2D fighting game engine designed by Elecbyte, written in C with the Allegro library.The engine was originally released in July 17, 1999. Beta versions of it were made to work on DOS, Linux and Windows platforms, distributed through their website. The engine allows users to insert created characters, background stages, and other game objects through interpreted text files, graphics, and sound compilations to create a functioning fighting game similar to commercial games. While the engine is set up primarily for fighting game development, several other game types have been developed using it, including shooter and platform style games. Officially, Elecbyte claims to have forgotten what the acronym M.U.G.E.N stood for, but the readme documentation states that its meaning referred to the days when the engine was meant to emulate shooting games as opposed to fighting games.The engine allows anyone to create characters, background stages and other game objects through interpreted text files, graphics, and sound compilations. It supports various types of audio formats such as MP3 and MIDI initially, although it can be configured to play various audio formats via Winamp plugins, such as ADX and OGG, as background music during gameplay or at other points such as an introduction or the select screen. The engine allows for most of the same type of functionality found in most any commercial 2D fighting games, up to and including close recreation of those games' characters and gameplay.Nowadays, though, almost all of the M.U.G.E.N sites have either not been updated since 2010, or have been shut down. Because of this, finding certain characters is almost impossible.
DOS and Linux versions
First released on July 17, 1999, M.U.G.E.N was initially created for MS-DOS. Development of the DOS version ceased when Elecbyte switched to the Linux platform in November 2001. For a time, Elecbyte had posted a request for donations on their site to legally obtain a Windows compiler to make a Windows version of M.U.G.E.N. However, the development group discontinued the project in 2003 and shut down their site. Later speculation pointed at leaks made public of a private Windows-based M.U.G.E.N beta that was provided to donators.
Windows version and subsequent hacks
The private WinM.U.G.E.N beta contained a two-character roster limit, locked game modes, and nag screens. With the beta leaked and Elecbyte gone, a "no limit" hack that removed most of these limitations was made available in 2004 by Rou Hei, followed by subsequent updates to deal with bugs and other issues. This version of M.U.G.E.N. is functionally the same as the last Linux release, though with subtle differences and unique issues, mostly revolving around proper music and music plugin support. Because of the changes between the DOS and Linux versions of M.U.G.E.N however, many older characters required at least the SFF files to be modified to show palettes correctly (notably on portraits) as well as some changes in how certain CNS script controllers functioned, causing some minor upset and those that could still run the DOS version in some form sticking to that, as well as DOS patches to downgrade characters to be compatible with the older version of the engine.In May 2007, a hacked version of WinM.U.G.E.N was released by a third party that added support for high resolution stages (like those seen in Guilty Gear X) at the cost of losing support to standard resolution M.U.G.E.N stages. Later that month, another hack was done to add support for high-res select screens. In July 2007 another hack created by Sion and Kung Fu Man based on the last high-res hack allowed for only the select screen to be high-res and not the stages. In December 2007, a hack from an anonymous source allowed both low-res and hi-res stages to be functional in the same build, requiring only a single line of code to be added to hi-res stages.
Elecbyte's website and the return of the M.U.G.E.N engine
In mid 2007, Elecbyte's site returned, though not without some controversy as to the legitimacy of it, as it only showed a single logo with Google ads on the side. On July 26, though, a FAQ was added to the site. This FAQ went on to claim that they would release a fixed version of WinM.U.G.E.N before major format changes in the next version, and noted the formatting changes would remove compatibility in regards to older works: "Do not expect old characters to work. At all."Despite some widespread agreement that the new site was a fake, things changed roughly two years later, when a new release candidate, MUGEN 1.0, was added to the site, with Open GL support as well as proper HD display options, victory quotes, improved (and growing) stability as a whole. The claim of widespread incompatibility of old works with this engine turned out to be false, as Elecbyte took steps to ensure that at the very least properly coded characters would not malfunction in the new engine (or would require minimal updates), though screenpacks are not necessarily subject to the same rule. As of January 2011, MUGEN 1.0 is no longer in the "Release Candidate" stage, and MUGEN 1.1 has been released on August 6th, 2013.
MUGEN Genesis (Created by Gamefreak202020. No longer very active.)
Phantom Gs (MOTVN and Hank Venture's community. Formerly welcome to the public; registration is now closed.)
Random Select (A large database for characters and stages. Currently home to the BIJIN engine, an offshoot of the MUGEN clone IKEMEN.)
Stupid Dope Mugen (Product of Crazy Koopa and MC2. Sadly not quite as active as the other places.)
Mugen-Infantry (A branch forum from the Guild, started around 2004 by DJ-Van, the guy who created the EVE Battle screenpack, and some other guy named Aztec Soldier who has since abandoned his admin duties due to a massive addiction to Halo. Most notable for its constant server downtime and maintenance throughout the years. Has figuratively gone through hell and back, as the entire site was shut down due to Aztec not paying the bills, but it was eventually revived on Blogspot. In 2009 a revolution broke out when the Random Insanity section was removed, which caused the formation of Genesis, as shown below. It has since been brought back, but with roughly half of its supporting members gone. The forum is currently back up and running.
The Mugen Fighters Guild (The basic start point for many MUGEN players. Highly recommended if this is your first time using the engine.)
MUGEN Motherland (PrinzJanus' Forum, formerly known as PrinzMugen). Built initially as an alternative to more serious forums, Motherland presents a more casual tongue-in-cheek approach to the engine, focusing more on the playing aspect than actual serious creation and testing. It reformed itself due to complications with the old hosting.
Trinity Mugen (Created by Vans, Jesuszilla, and Fusion around 2005, it is as its name suggests. Home of many a worthwhile character and will provide hosting services if necessary). Forum is not much active, most of the action is at the IRC chat.
http://mugencharacters.ucoz.com/ - One of the larger databases of MUGEN characters available today, it has just about every character ever made, including some that are otherwise all but impossible to find at all (other websites just list them as being "offline," or worse, they're only hosted on Phantom Gs). Unfortunately, as a corollary, it has just about every character ever made. Additionally, it hosts its own copies of everything, which annoys no small part of the community; CTRL+F "Warehousing" below.
http://mugenchara.blog.shinobi.jp/ - A Japanese MUGEN blog, with a character/stage entry added nearly everyday. It only links content to their original downloads. A translator tool is required for most users.
For the sake of not turning this article into another list of character tropes, please avoid adding entries for characters which aren't exclusive to Mugen, as tropes associated with characters from existing series can have theirs listed in their series' page.
This engine, its community and sometimes games made with it (including itself) provide examples of:
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Accentuate the Negative: The defunct Doki Doki MUGEN review site. Other creators have been known to indulge in this at times when they give feedback.
Aerith and Bob: When you have a crossover between many games, this is going to happen.
A.I. Breaker: Some characters, such as mob-type characters and massive boss characters, have a tendency to confuse AI controlled characters. One Kung Fu Man edit, AK Man, invokes this trope by completely shutting off opponent AI and leaving them helpless, and even then there are a few characters that can still defeat him.
Amazing Technicolor Battlefield: When projectiles, clothing, and the background tend to be all the colors of the rainbow, it's bound to happen. Even drab urban settings or grim Mortal Kombat stages can get quickly colorful.
Amazing Technicolor Population: With custom palettes, this is possible for just about anyone. The character literally named "Ms. Fanservice" (actually a joke edit of Yoko), for example, has blue, dark blue, red, and gray-skinned schemes. That's not getting into the characters who are already technicolor, or extremely broken examples like the infamous "retarded" Peter Griffin (who has a new color scheme for just about every sprite thanks to a lack of any loaded palettes).
Assist Character: Some characters have built-in assist characters (usually referred as Strikers like in King of Fighters), some of them like Juza who had them in source game, but the majority of characters with built-in assist characters have them because of the engine's limitations.
The Uno Tag System lets you do this with many characters.
Attack of the 50-Foot Whatever: Doable, in the vein of Apocalypse from X-Men Vs. Street Fighter, with proper application of art and hitboxes. Bizarrely averted with Godzilla and Gundam fighting characters... buuutttt there are some stages that allow you to do this (with, strangely enough, Godzilla and Gundam stages). Same goes with EVA and Primal Rage characters.
Author Filibuster: Some of the MUGEN videos have this problem, as do people creating custom characters - especially from scratch. There is also the popular practice of coding a character to crash against opponent characters the author does not like, or making videos solely about beating up a character they hate.
Back Stab: Literally for The_None's Segalow, who has a level 3 super where he grabs the opponent and if he does so he slashes them. If its done when they're facing him it does moderate damage, but if it connects from behind, it does MASSIVE damage. He does have elements of The Spy after all.
Badass Adorables: Ranging from moeblobs of various anime (Haruhi and Konata were massively popular in their heyday) to, of course, the new batch of My Little Pony.
Badass Normals: Anyone who doesn't throw fireballs/shoot lasers/doesn't mutate/isn't magic can beat up homocidal robots, killer aliens from outer space, evil psychic projections made from two mutants that happens to be bigger than a skyscraper, and actual Gods. Kung Fu Man is one of the normals, in that he doesn't even have a single projectile attack.
Beyond the Impossible: There are characters who can win the battle before the match even starts, something that never occurs in any other Fighting Game. It is also a literal breaking of the game's rules, in the sense that their code overloads the game that the opponent fails to load and is thus defeated.
The Computer Is a Cheating Bastard: Prevalent in some characters to an uncomfortable extreme. One example is certain characters not requiring to have a minimum level of power to do their hypers when controlled by the AI, but do require it when controlled by the player. (Although this could be a simple bug in some cases.) The good news is that some of the more diplomatic creators will include multiple levels of AI for their characters, and for the rest, MUGEN's customizability lets you curb the more insane AI yourself by tinkering around in the character files.
Crossover: Very often used for this, although gameplay styles won't necessarily mix well, particularly when Guilty Gear, a game known for being much more notoriously fast-paced and complex than other fighting games (on top of ludicrously cheap AI) is involved.
Damn You, Muscle Memory: The possibility of a MUGEN build having characters coming from different source games (complete with distinctive control schemes of such) tends to get some players mixed up when getting to know or use new characters.
Death of a Thousand Cuts: There are many characters who's attacks will hit the 999 combo meter. It's mainly overpowered characters.
What's a little funny is that in Daniel's readme, his goal is "to achieve 1,000 hits in MUGEN."
Both Chuck Norris and Oni-Miko-Z (and countless other "unbeatable" characters) have fallen to the Debugger character, two floating strings of numbers that "delete" the opponent's root file, causing them to be read as nonexistent and dead.
Demoted to Extra: The BlazBlue characters remain almost entirely unaccounted for here. So far, there's a version of Jin known as Ares who plays like a bad Ky Kiske cover band and a recurring meme in The_None's Segalow where he backstabs Ragna in the prefight intro. Recently Hakumen, Tsubaki, Hazama and the original Jin (with ice) have been ported in and Neat Unsou has released a Calamity Trigger-accurate Nu-13 which has been well acclaimed by many. The lack of Blazblue conversions is caused by the large size of the sprites (though there are ways around that) and that adapting the sprites to the proper size does not necessarily make it possible to translate all of the physics and mechanics properly.
Depending on the Writer: If about two or more makers share the characters they've converted, don't expect them to be both exactly the same.
"Warehousing" is the practice of hosting a character on a website without the creator's permission. In some MUGEN circles this is regarded as a disrespectful and dishonest practice, while others simply aren't concerned about it.
The second one, much more subject to ridicule, is known as "spriteswapping". The "creator" takes another character, and replaces the original character's sprites with his own sprites. In particularly bad cases, the spriteswap will retain the base creation's gameplay elements even if it doesn't match the spriteswap's playing style. Many spriteswaps also tend to have jacked-up stats, making them cheap and over-powered, like so.
XCB, a once-renowned creator, attempted to copy-protect one of his characters against spriteswapping by, at the start of the match, checking to see if the creator and/or name had been modified in the fighter's .def file. If it detected a change, then it would stop the match and throw up a short Refuge in Audacity skit featuring Pac-Man before displaying "STOP STEALING MY SHIT!", and crashing the program.
It gets better. When XCB left the community, he left behind one unfinished character called Blaque, who was supposed to be the canonical sister of his character Tetsu Yatogi. As his parting gift, he made a separate, "special" version of that character which he leaked anonymously. When opened, it turned out to be a screamer showing loads of NSFW content before flashing "Have a nice day!" in comic text. The real, unfinished beta of the character was eventually leaked anyway.
Subverted in the case of sprite-ripping characters from games (such as Ryu) and using them in MUGEN. Capcom was asked about this early in MUGEN's existence, and the company stated that they consider it a form of fan art (so long as no one sells the characters, of course). Pretty much every other company has followed Capcom's attitude.
Ditto Fighter: Ditto is actually in this game now, and it transforms into other pokemon as its attacks.
Rikard attempted to deconstruct this trope with Slightly Pissed Off Ryu. Not only did it fail, but Rikard became pigeonholed as the creator of this character rather than his original characters, much to his displeasure.
Iggy's throw has his Stand grabbing the opponent and Iggy jumping up to said victim and farting on his face.
Fighting Clown: There are quite a number of characters that look and act silly but otherwise play like a normal one. Examples include Dancing Banana, many of The_Noone's characters (especially Dee Bee Kaw), DDR/Telechy's cartoon characters, etc.
From Bad to Worse: EvilSlayerX5. First, he used to be some loner who disliked accuracy. Then, after he created his less than stellar Rugal_E which multiple people criticized as a game-breaking and buggy character, it all went downhill from there. He actually believed at one point believed that there was a secret government controlling the masses to hate him and his characters.
Fusion Dance: Segalow is a weird fusion of Seth from Street Fighter IV, Rugal (uses his Capcom VS SNK sprites but with the moustache shaved off) and Lazlow of all people as one his voices is taken directly from Grand Theft Auto 3, his KOF XI lifebar port is Lazlow's Vice City artwork and his flavour text on The_None's site is a direct transcript of some of Lazlow' dialogue from GTA 3. He also has elements of Ray Park who played Rugal in the KOF movie as well as Darth Maul (His big port is KOF movie Rugal and he has a super involving a double-bladed llightsaber.) and The Spy. Oh and he also has The Spy's Dead Ringer.
Game-Breaking Bug: Certain matchups can lead to one character being unable to land a single point of damage on the opponent, both characters being unable to damage each other at all, or outright malfunctions in the engine, due to the different codes used with each character and/or sloppy coding.
Gone Horribly Right: Meta example. So you want something where every fictional character you ever knew and loved fights? Here you go. Unfortunately this also resulted in many of said characters being cheap, poorly made, unfinished, and/or not at all true to their original game. That, or horrible, horrible imbalance in fights between different styles of fighters.
Gorn: Several characters in the MUGEN roster, such as those from Mortal Kombat, are fond of gory ways of finishing off opponents.
Inevitable Tournament: it had to happen. Some MUGEN forums hold tourneys for fun. While most follow a standard format (usually 1 vs 1 or 4 vs 4), some have fun twists on the genre.
Instant Death Radius: Oni-Miko-Zero. Literally. Put her up against any character (save for a few) and that character is DEAD even before the battle starts...
The "Debugger" character uses a code that somehow deletes the opponent's root state, causing them to be read as nonexistent and thus KO'ed before the round starts. So far, it can beat Oni-Miko Zero and Chuck Norris with no effort, and is possibly the cheapest character ever.
Did somebody say "Salvation Orochi"? Because I think somebody said "Salvation Orochi".
The latest versions of uber-cheap characters (known as "Postman" or "Secretary" characters) run an .exe that affects the game such that only characters with their name are allowed to win.
Internet Mimic: Back in the day when Judgespear was still active, since the main characters he used were Homer Simpson and Peter Griffin, he made most newcomers to grab Homer and Peter (a practice now frowned upon by more experienced players).
Jack of All Stats: Amongst examples, there's Kung Fu Man, a character that comes with any downloaded copy of MUGEN (mostly as a base for making characters, and a coding example) that eventually became the mascot of the engine.
Jerk Ass: A prominent character trait of certain community individuals.
Kyubey. He doesn't attack, defend, or even move after starting the match. Justified in that, considering what he actually does in the series, he deserves every living second of pain. It also fits since he's never seen in-universe as capable (or willing) to defend himself, though that doesn't matter as he's immortal.
There's a version of him that does fight. It's not all that good, though.
Beatdown characters in general, like the above-mentioned Kyubey. These practically do nothing but stand in one place and take damage from everything until they die.
Lester, who has weak attacks, low defense, and has a "move" where he runs from his opponent in fear.
The NES Silver Surfer. He's incredibly weak, can't even turn around, and dies if he touches anything, even the edge of the screen. To make matters worse, he automatically loses the first round.
Flappy Bird. It dies if it gets hit or if it hits the ground, gains power very slowly, and if it survives long enough to get 3 power bars, it can use a Limit Break where both it and the opponent go through the Flappy Bird game itself. This deals a lot of damage to the foe if they don't avoid the pipes... but it also kills Flappy Bird if he fails to avoid.
Jump Scare: The_None's Giygas uses this extensively.
Kiai: Being a fighting game engine, there are many examples. The most particularly notable one is the JoJo's Bizarre Adventure "WRYYYYYYYYYYYYYYYY!" (Used when anybody uses the Steamroller or when Chuck Norris drops the sun on his enemy.)
Lazy Artist: Rather common, especially when new Shotoclones are involved. However, this is sometimes justified, when creators use characters as bases for their distinctive creations (e.g. the majority of the MvC-styled Mega Man characters, which use Mega Man as a base).
Wobbuffet. Like its original source, its only form of damaging the enemy is via Counter Attack. However, the power of its counter against physical attacks increases if it takes a hit when swinging, making it able to kill otherwise-broken characters in one hit. And it gets leftovers and Shadow Tag as moves. Finally, it also gets Destiny Bond, which K.O.s the opponent instead should Wobbuffet get K.O.'d when the move is active.
Gay Bahamut/Primeus, The God Of Retarded Characters by RicePigeon, most of whose attacks involve notoriously "retarded" characters.
There's also Giygas/Ozma, created by fhqwhgads7 and supposedly inspired by Primeus, which is an April-Fools'-joke-character-turned-boss. It's basically a gigantic floating jawbreaker that starts off with Giygas' attacks... and then imitates various Youtube Poop characters as it loses health and layers.
Vans' Rock Howard, who has the voice of Urien and whose MAX2 super move destroys the universe, crashing your program in the process.
Omega Tiger Woods, who can and will soundly pummel almost any character he comes across as long as that character isn't another Omega Tiger Woods. Where does he get that Shrimp Bus from, anyway? He's intended to be an SNK Boss-type character... just bizarre.
Similarly, Omega Tom Hanks, who turns the fight into a game of Bullet Hell by sending DVD covers of his hit movies after you.
Someone made a version of Mario for MUGEN called "NES Mario". He can only attack by jumping on enemies and he dies in two hits (if you don't press the button to turn into Super Mario again at the expense of some of the lifebar). However, there's something that makes him lethal: Fighting game characters flinch when hit, Mario does not. If you get a window of opportunity, you can just keep on stomping your foe and finish them off in less than a minute.
Speaking of Mario, someone remade the first level of Super Mario Bros. Your hilariously oversized character will still be one-shotted by Goomba and pits, especially if they have limited jump physics.
Saggot, aka Bootleg Sagat. An edited Sagat that plays like the infamous Street Fighter II bootlegs. What this means is a whole new level of Tiger Shot spam, ridiculous comboability, and he even crashes MUGEN on a regular basis. To further rub salt in the wound, his theme from Street Fighter 1 perpetually plays during his fights, overriding your music, and his victory pose references the famous Cornflakes line from the Street Fighter cartoon.
Other Street Fighter bootleg characters that end up being dangerous include Koryu (heavy projectile spamming much like the infamous Koryu edition), Broken (similar to Koryu), and Viga (whose moves can do serious damage).
"Ms. Fanservice," who seems like a heavy edit of Yoko who uses other Ms. Fanservices for her moves, and an entirely different moveset. It sounds like a run-of-the-mill gag character, and is overall tamer than most characters on this list, but she has extremely aggressive AI, able to take down many other characters who aren't outright cheap. Including the original Yoko she was based on, who isn't a cakewalk herself.
Loads and Loads of Characters: There are so many characters out there to download and play with. The wiki itself lists somewhere around the range of over 2000 characters from all kinds of fighting games and miscellaneous media. Granted a large majority of them are Shotoclones and Sturgeon's Law is often in full effect when downloading certain characters.
Luck-Based Mission: Whether Bokosuka Wars wins or loses is purely luck, just like in the original game. It's also the only way he can give or receive damage. If he can't reach the enemy's hitbox (assuming the opponent even has one), if the opponent is immune to grapples, or if he fights himself, it will be a guaranteed draw game.
Quite a number of them. An original character example is Omega Tiger Woods who can't block at all but has a crosshair that drops missiles (and a claw arm) on the enemy.
Otherwise normal characters can become this if they are configured to under certain palettes. ShinRyoga and Neo Ankh's Mario has a "ghost mode," where he is completely invincible and has a quickly charging power meter, but his health depletes fast as well.
Ms. Fanservice: A girl literally called Ms. Fanservice by Kelexo. She's an edit of Warusaki and Kabao's Yoko Littner with cameos from the usual suspects like Felicia, Dizzy, Chun-Li, Elena, Yuri Sakazaki and King.
Mythology Gag: Dcat's Krang has attacks, quotes, and even colour palettes from various shows, comics and video games in the TMNT franchise (and in one instance, his crossbow move is taken from a kids' colouring book).
Nigh-Invulnerability: Alot of the characters have either zero hitboxer or seemingly infinite health.
Nintendo Hard: A lot of AI patches go here. For a specific example, the work of Misobin_ISM. He turns mild mannered, but still challenging, characters into absolute monsters. His patch for Vergil basically pits you against an encyclopedia of his combos, Dio lays you out with some crazy tandems and abuses his teleport while defending, Geese will counter all of your moves and force feed you a Deadly Rave, and Shin Akuma is as insane as you would expect. There is also Hutano, who basically unlocks the true power within 9's Melty Blood characters and shows you some of the most nightmarishly evil combos ever seen.
Muteki's Guilty Gear characters are built with aggressive AI that takes full advantage of the computer's natural advantage against human players. It blocks most attacks without a second thought and links together very long strings of attacks and supers to make sure that the human player can't fight back for more than a second, and with Guilty Gear's extremely fast gameplay, tends to turn anything not incredibly fast-paced into chowder.
For a non-fighting example, pitting fhqwhgads7's The Kid and Yukari Yakumo together will start the match with The Kid in a scrolling obstacle course. Keep in mind that like in the game, The Kid dies with one attack, and you can't fight Yukari unless you get through the course. Even then, the match simply becomes a boss fight against Yukari... and Primeus.
For a long, long time, Sander 71113's Wolverine was known as an absolute monster and the bog standard for players looking for a challenge.
No Ending: Most characters do not have ending storyboards for completing arcade mode. Or intros, for that matter.
No Fourth Wall: In one of her winquotes, RicePigeon's Yukari Yakumo recognizes M.U.G.E.N as a computer program, and how amazing it is to merge diverse worlds together, then concludes that humans must really have been inspired by her.
In general, it's possible to edit winquotes, so any char can play this straight. For instance, there is a version of Rocko who comments that M.U.G.E.N day can be a very dangerous day.
Norio Wakamoto: There's CV-Wakamoto, some... thing with Wakamoto's voice and moves taken from characters Wakamoto has voiced. A edit of Kung Fu Man was released with, you guessed it, Wakamoto's voice. It had most of the moves of Wakamoto's characters, and is incredibly broken.
Similar to her, Debugger does this to its opponent. Except that his works on pretty much everything (Oni-Miko-Z included).
Death Note: Light Yagami writes his opponent's name in his Death Note as soon as the match begins. Fans of the series can probably guess what happens next.
Zeeky H. Bomb has two of these. One (Random H-Bomb) only works as a counter, and the other (Zeeky Boogy Doog) severely damages Zeeky himself.
Pingu's most devastating attack has him sink into the ground as the lights go out and he calls to his opponent. Then, the lights turn on and he reappears in front of his opponent, wings upraised. Instant KO! His Shun Goku Satsu is usually a KO, too.
The Space Invader has this both ways. If his laser gets you, you're instantly vaporized. If you hit him once, he's instantly vaporized.
Andres Borghi's characters have Awesome, but Impractical one hit kills. They take 3 special bars and are blockable. In addition, in their original form they were Desperation Attacks only usable when very low on health, and the updated versions in the full game are finishing moves instead, only usable on an opponent who is low on health.
Noroko sends out a spectral version of herself forward. If this hits, she will fall to her knees and start crying, the opponent will come by to see what's wrong. and then a video plays where she either reveals her featureless face and reaches forward with a hand, or opens a disturbing-looking mouth and screeches. The opponent will immediately die, either of sheer fright or maybe having their soul stolen.
Peketo grabs then throws the opponent into a spiked wall, then decapitates (or just slashes) them with a knife.
Hashi grabs the opponent and feeds them some kind of seed that turns them green. Presumably that makes them taste better, for he then morphs into a huge Man-Eating Plant and devours the victim alive.
Slot Machine has two: A clone of the Shun Goku Satsu from rolling Toadma), and a lazer beam that goes across the top of the screen from hitting Quick Man until after either the match ends or the machine is defeated in a team-like mode like survival or... a team. (The beam stays at the top of the screen even in later rounds.)
Original Generation: While a popular use of the engine is adapting characters from existing games, many people have created original characters using the MUGEN engine - SeanAltly is a prime example, as well as Andres Borghi, Reuben Kee, Kung Fu Man, Aiduzzi and Rikard.
Overly Long Gag: Renowned MUGEN creator aokmaniac13 is guilty of this in his 'Mind Games' video series. Generally, they focus on a major flaw in the character's AI, such as never guarding low or behaving awkwardly when he does something simple, like crouching. As you might've guessed, they run for all 99 seconds on the timer, and for two rounds to boot.
Panty Shot: Potentially any girl wearing a skirt; whether they play this straight or wear a Magic Skirt depends on the game they're ripped from, the franchise they come from, and/or the character maker's personal preference.
Paper-Thin Disguise: EvilSlayerX5 as SilverJeric. Not surprisingly, everybody saw through it...
Power Creep, Power Seep: Tends to happen when creators don't strictly adhere to the idea of converting characters exactly as they were in the source game. Seravy (the "creator", not the character) actually tries to avert the creeping trend, but is often ridiculed for the results.
Pragmatic Adaptation: While most characters are either labelled as accurate but aren't, there are a number of characters that are deliberately not meant to be accurate, such as CCI Ironmugen's Ryo or The_None's Shaq. In some cases, accuracy may NOT be a good thing.
Press X to Die: The F1 key does this to player 2. For player 1, it's CTRL+F1.
Rage Quit: Parodied with Rage Rock, whose Hidden Desperation Move crashes the game.
Schizophrenic Difficulty: In addition to the Lethal Joke Characters covered above, there are several characters, or at least versions of characters, who are much harder or easier to take on than you would think. For instance, Alucard's AI is pretty easy, but Team S.M.R.T's Homer Simpson can be a tough fighter, especially if he enters Beer Riot Mode.
Self-Deprecation: When not doing the below, Rikard, the Italian creator who made several characters heavily edited from KOF and Slightly Pissed Off Ryu (for more details on the latter, see Take That entry below).
Serious Business: Despite appearing to be the go-to answer to questions like "Who'd win in a fight between Optimus Prime and Bill Clinton", a vast majority of the community can take certain matters way too seriously, such as the "cheapness" of certain system features.
The_None released a version of Kishima Kouma dubbed "Shadow Kouma" that at first appears to be a perfectly innocent custom take on the character. Then you actually see him in action and he turns out to be a Shang Tsung type fighter who transforms into every character The_None has created for his attacks. He does have a handful of unique moves, including a team up with Ralf Jones and JoJo style tandem attacks.
Before that, there was Cerenas's Sihon (who transforms into various Samurai Shodown characters) and the collaboration between Andre Lopes and Ryan Kerns in the form of Mugena (who mainly transforms into various female characters).
Shang Tsung himself as well. OMEGAPSYCHO's version deserves special mention, as he managed to make him able to transform into nearly every MK1 character but Goro. Juano's Shang Tsung goes this way too, having every MK 2 character, including Jade, Noob Saibot and Smoke, but excluding all bosses.
Numerous characters use Mortal Kombat-esque fatalities or otherwise incorporate something from the game, such as Most_Mysterious's Dink Smallwood speaking some of Shao Khan's lines, or the "Shao Mario" from Slot Machine, which is Mario's Super Mario World-appearance given Shao's voice.
The_Nones already made Blizzard a bit silly, with his intros having him beat the shit out of "Stone Cold" Steve Austin or descend from a Rampage building. However, his palette swap, Chaos, inserts random farting noises as a soundtrack and uses Retsupurae clips.
The use of Silly soundpacks, such as using My Way Entertainment's infamous Juggernaut soundclips for, uh, Juggernaut.
Kung Fu Man's intro and ending storyboards that come with the engine by default qualify, looking like a kid's crayon drawings.
Most_Mysterious's (of Omega Tiger Woods (in)fame) entire creationhood can be basically summed up as this.
The Dancing Banana also counts in a way, what with being a rather pixelized character, but the reason for this is because his graphics are based off the original emoticon.
Summon Magic: Some characters do this as a super attack by calling in a reinforcement to perform an assist (see Kamek in the Shout-Out entry above). For example, Hatsune Miku takes this Up to Eleven with her super singing attacks - if she sings a soundtrack from a well known franchise, a character from the franchise comes in to perform the assist. And given how manythere are...
Super Move Portrait Attack: The_None's Shadow Kouma deserves special mention, for that he has a super move that takes this trope literally. Yup, the said move involves the portrait itself hitting the opponent.
Zangyura, a bastard child of Zangief and Godzilla of all people has a "Gorbachev" mode.
And his latest (so far) creation, Zangeese (who also comes with an optional Athena movelist....with the voice of M. Bison).
He has a Heavy D! there, which seems normal....until you hold start and he gains K's moveset.
3ha's Genjuro Kibagami uses a mixture of the Slash/Bust system of IV with the gameplay of V Special, complete with Zetsumei Ougi. Holding start while selecting him, however, lets you control his frog, which has M. Bison's moveset and voice.
Rare Akuma is the mother of all Take Thats to badly done "Shin", "Orochi" and "Evil" edits of many characters. He has an abundance of special effects, is effectively immortal, and can kill most characters in the space of a few seconds.
There's an entire full game being made with nothing but Akumas with completely different movesets. The creator of the project, Basara, admitted he's doing it because he's sick of all the Akumas going around.
MUGEN Gangbang/Gankbank/Tennis, anyone?
Rikard's most prolific creation is Slightly Pissed Off Ryu, a parody of the various Shin, Evil, Orochi, Violent and Holy Ryu edits on the internet. Rikard's "story" basically sets Ryu as a McDonald's bum, depressed and physically out of shape after finding his wife Sakura cheating on him with Akuma (he has appropriate, and hilarious, victory and winquotes against both of them). His Hadokens are usually a pathetic short range burst, his Shinku Hadoken may u-turn RIGHT BACK INTO RYU'S FACE, he falls flat on his back after a Shoryuken, he sometimes breaks his ankle when he does his trademark Hurricane Kick, and one of his other attacks has him lobbing either a McDonald's meal or M. Bison's corpse at them. Most Ryus run on graphics over gameplay. This Ryu? Runs on pure Rule of Funny.
Arpa's Casual Evil Ryu is a big yet sly Take That to Infinity Mugen Team's "Eternity of Heroes" character template and its many, many flaws, amongst other things. He outright states as such in his True Readme...which is written in Saurian and also features a Take That to that game.
That Wacky Nazi: EvilSlayerX5 revealed himself as that after he changed the background of his youtube profile into a swastika. Or MC2 just made people believe that.
The game's still popular in Japan for this reason, and loads of Pixiv fanart based on bizarre matchups (and even pairings) have occurred, spawning things like a cross between Alice Margatroid and Cable due to their reliance on lasers.
There is an AI-only character called "Biohazard" that is basically a huge swarm of zombies, crows and dogs that all share one life bar, and killing enough of them eventually summons a Tyrant. The Alien Queen's default palette is also this; she does not appear at all in this mode, but instead sends a swarm of Alien drones to attack you, and the match only ends when you've taken them all out. The Mad Gear Gang are also available as an opponent.
There's also the "Strength Training" minigame, which pits your character against a swarm of Beat 'em Up-style Mooks, and is sometimes used by series creators for mook fights.
With some luck, you can hack stages like Super Mario as an opponent, resulting in an odd variant of this.
An experienced coder can code this onto any character, making that character attack in a Zerg Rush of easily-defeated clones. A good example and possibly the Codifier of this would be Most_Mysterious' Rox Howard Clones.