Butt Monkey: Both Meat Boy and Bandage Girl get abused quite badly.
Doctor Fetus gets this too, especially given the intro. "Nobody likes Doctor Fetus, and that's why Doctor Fetus hates you!"
Effectively, every single character that appears in a cutscene is one of these. Especially the tragic squirrel, who is the lone survivor of the forest fire, is attacked by a rogue flying buzzsaw, is vaporized by a nuclear explosion, and STILL manages to come back at the ending cutscene, totally beaten up. Most bosses are also killed off in a rather dark-humored way. They all have a happy ending in the final cutscene though.
Creator Thumbprint: It's not Edmund's first game which features a character in a developmental stage of a life cycle.
Death by Irony: Both games end with Bandage Girl, who had been kidnapped and punched repeatedly by Dr. Fetus throughout the game, stomping Dr. Fetus to death.
Level Editor: Meat Boy featured one. Super Meat Boy gets one for the PC version. A prototype devmode was accidentally left in the game which resulted the creation of user-generated content much earlier on.
Malevolent Architecture: Who puts buzzsaws in salt factories and skyscrapers anyway? (At least the forest sort-of made sense as an out-of-control logging operation.)
As you play through the Hospital, you'll begin to wonder where all these syringes come from, and why they're stuck to the walls and ceiling, needle-down.
Marathon Level: Some levels such as Omega, compared to the norm.
Nintendo Hard: And get used to Meat Boy's speed. Although those who think the game isn't hard enough, in Super Meat Boy, there is a more difficult counterpart to each level.
Cotton Alley. The Kid's levels. Dark World Rapture. Have fun, kids.
The Expert Remix chapter (which contains versions of main game levels that are even harder than the Dark World) means even more controller tossing.
The Kid's 2011 Christmas features four difficult levels (though one can be broken easily by turnstile hopping). The fifth however asks you to traverse the original Kid's level backwards.
Resurrective Immortality: Meat Boy is a One Hit Point Wonder, but reforms within one or two seconds, much to the frustration of Dr. Fetus. And not just during gameplay, during cutscenes too!
Shout Out: The game has a large amount of them, which is expected from an indie game.
The Flash game opens with Dr. Fetus stealing Bandaid Girl ala Ghosts N Goblins. This is also present in Chapter 7 of Super Meat Boy, except Dr. Fetus captures Meat Boy instead. Super Meat Boy likewise begins each chapter with a re-enactment of the opening to a different game:
Chapter 1: The CPS1 editions of Street Fighter II (The World Warrior, Champion Edition, Hyper Fighting)
Furthermore, the characters that say that Bandage Girl is in another Warp Zone are also shout outs; for example, the Ninja from Nikujin or Captain Viridian from VVVVVV.
When you successfully complete a level with a bandage collected, the message "Bandage get!" appears, referring to the Japanese version of Super Mario Sunshine.
One of the glitch worlds resembles an airship from Super Mario Bros 3 — complete with fixed-speed sawblades simulating auto scrolling.
The sound when picking up a key (when not in a Warp Zone) is the same as from Atari's Gauntlet.
The respawn after death literally take less than a second and is automatic.
The levels themselves are short, ranging from 15 seconds to 90 seconds, so in the quite likely event you die, you don't have to go through too much again.
Various little side-quests when you get too frustrated with the main game, like beating past levels in record time, collecting bandages to unlock new playable characters, or playing through retro-styled "warp zones".
When you finally do beat a level, the game then shows you a replay of all your past lives doing the level simultaneously, which is good for showing you where the hardest parts of the level were. It's also kinda hilarious to see a cloud of Meat Boys get shredded to half their number by a giant saw.
Awesome, but Impractical: Steve and Meat Ninja, whom cannot be used to complete levels legitimately or earn achievements.
Bait-and-Switch Boss: Brownie, who was supposed to attack you first, but when Dr. Fetus starts flooding the room with salt, you both start racing to escape it.
Boss Subtitles: CommanderVideo, Jill, Ogmo, Flywrench, and The Kid all get these. (Flywrench does it a bit differently — instead of a freezeframe and displaying his name and the game he's from, it's simply a black screen saying "Launch Flywrench.exe?")
Bragging Rights Reward: The final Dark World level is appropriately named 'Brag Rights'.
The warp zone that unlocks The Kid being one of the most brutal set of levels ever put in a game. But what were you expecting from a Super Meat Boy / I Wanna Be the Guy crossover?
There is an extra, very hard chapter unlocked by beating the game.
Bullet Time: CommanderVideo in his introduction video.
The Cameo: Some non-playable characters make a cameo appearance too, like Darwinian from Darwinia or the boy from Limbo.
Chainsaw Good: The first boss has it, along with regular buzzsaws of doom.
Cheat Code: Required to play as Brownie, a Goo Ball (Steam version only), and Tofu Boy.
Cluster F-Bomb: The final Light World level is appropriately named 'Four Letter Word'.
Context Sensitive Button: Dr. Fetus' single-buttoned Handy Remote Control is this, as it can to anything from summon a boss monster to turn on machinery to throw at Meat Boy to send him off a cliff.
Cranial Eruption: The 4th boss gets two of these during the fight. Since he's made out of dead meat, they're rather blocky.
Crapsack World / Crapsaccharine World: If you aren't dead, you're about to be, and everything kinda sucks while you're alive anyway. A squirrel can witness his whole family die, only to be killed by a random saw blade. He gets better, but only in time to be killed by a nuclear explosion to get a bit better again during the ending. Heck, even Dr. Fetus is only evil because everyone hates him! Also, most of the locations Meat Boy visits seem to be in ruins.
Creator Cameo: Complete one of the minus worlds and you see the creators of the game make an appearance.
Crutch Character: Commander Video, sort of. His float makes it easy to clear levels and get bandages in the first two chapters, but he's very slow and his jump is one of the lowest in the game. Many levels later on are impossible to clear with him due to his flaws. However, it's still somewhat possible to get some bandages easier in later levels.
Cut Song: The Dark World of Chapter 5 has an unused theme. Same to second part of the boss level.
Dark World: Each of the main levels except the boss battles (not including Chapter 6's boss) has a dark world counterpart. You don't know why the other ones are called light worlds until you play these.
Deadly Dodging: A few times it has to be done. For an example, to allow turrets open up the passages. The fifth boss fight requires you to lure the boss to his death.
Deadly Rotary Fan: Several levels have giant fans that can propel you through the air. Get too close to the blades, though, and SPLORCH!
Deliberately Monochrome: Some of the levels (and the entire 6th chapter). Monochrome or dichrome levels are more frequent in Dark World.
Disney Villain Death: Subverted — Dr. Fetus appears to have died after being defeated Super Mario Bros. style in the final boss level, but then he pulls off a Taking You with Me by activating a self-destruct. After Meat Boy and Bandage Girl escape, Dr. Fetus reappears and hits Bandage Girl over the head repeatedly.
Double Subverted — He actually accomplishes nothing by hitting her, which he soon realizes and falls to the ground. Then he's stomped on. A lot.
Distressed Dude: Eventually, Dr. Fetus decides that he has had enough of capturing the girl and captures Meat Boy instead.
Doppelgänger: Meat Boy has four and counting. And that's just playable characters. There's Brownie, who's a traditional Dark Reflection type doppelganger, Tofu Boy, pretender to the throne turned pathetic Joke Character and star of Peta's ill advised parody game, Meat Ninja, Meatboy as a Future Badass from the year 20XX, and most recently, Potato Boy, an April Fools joke and Portal 2 tie in who's afraid of girls. Not to mention the fact every time meatboy dies, his former body lives on as a Meatboy zombie as seen in Hell and Rapture, of which there are doubtlessly thousands. Then if that weren't enough, the Meatboy zombies can merge together to form a colossal Meatboy golem called "Lil' Horn", which serves as the game's fourth boss. Despite all this, there is not yet a Robo-Meat Boy.
Double Jump: Some of the unlockable characters can do this, and one can even triple jump.
In the Xbox 360 version, there's an extra chapter called "Teh Internets" (unlocked by collecting 20 bandages) that has 5 sets of 20 levels.
Dummied Out: In the PC version, there's a primitive level editor, a complete character select, and a playable Dr. Fetus, complete with functioning rocket launcher.
The End... Or Is It?: The complete ending shows that Bandage Girl is pregnant with an evil fetus. Dun dun duuuuuun!
Everything's Better with Rainbows: If, for some reason, you don't like playing as Meat Boy and dripping a trail of blood everywhere, one of the first characters you can unlock is Commander Video from the BIT.TRIP series, who has an 8-bit rainbow trail.
Evil Knockoff: Brownie, who is designed to look like Meat Boy, but instead of meat is made of Dr. Fetus' poo.
Game Breaker: Deliberately invoked - Steve? from Minecraft can dig through walls and place block in midair to stand on, allowing him to completely skip most hazards. As such, you cannot earn achievements while playing as him.
In one of the early levels, it's possible to get bandages over and over, resulting an incorrect percentage on the game completion. It also had a save file crash problem when it came out. The bugfix is still awaiting approval.
When PC port came out, many players also had some serious bugs ranging from bosses not appearing to not being able to start the game at all. Development team started to fiercely fix the glitches so it got 9 batches of bug fixes within 9 days.
Unfortunately, the use of variable framerate physics makes the game so glitchy that it is unplayable on performance-challenged computers.
Handy Remote Control: Dr. Fetus uses this quite frequently which does different things. Also parodied in one cutscene where Dr. Fetus pretends to be about to press it, only to throw it at Meat Boy.
Heh Heh, You Said X: If you Alt+Tab while playing, you will return to your computer's desktop with the game minimized. If you try to bring it back up again, you will sometimes get an error message stating "that the game has crashed. A mini-dump (heh heh) has been sent to the developers."
Homing Projectile: A few of the turrets fire these. Although their homing abilities aren't the best, they make up for it with projectile speed.
Also, Dr. Fetus' bazooka. While its projectiles are slower and smaller, their homing abilities are much better.
Interface Spoiler: Shows the number of chapters in the game. There is an extra chapter indeed after beating the first main 5 chapters + epilogue chapter.
Joke Character: Tofu Boy, a Take That to a Meat Boy parody by PETA. He's the slowest character in the game. No special abilities, and he can't jump to save his life.
He can't even beat the first stage — he can't jump high enough or move fast enough to reach the platform with Bandage Girl, even from the high cliffs on the side — and can only just barely beat the second stage.
Kick the Dog: Meat Boy in the ending scene of Chapter 2.
Meaningless Lives: Averted in the warp zones but played straight in the Minus Levels; since you only play one long stage at a time (as opposed to three in a warp zone), lives seem to serve no purpose other than to annoy the player with loading screens.
Medium Blending: Creators wanted to give art shifts opposite of Ren and Stimpy (where characters and everything else get extremely detailed in closeups) so in-game graphics where everything is distant is drawn more realistically, but menus and cutscenes are drawn in cartoon style. In-game characters, however, are drawn in very pixellated style.
Minus World: Deliberately used. Bandage Girl starts glitching sometimes when you replay levels in a chapter where you've beaten the boss. Reaching her when she's in this state unlocks that chapter's Minus World.
Mood Dissonance: Cotton Alley. The background is pink (very bright in Dark World), a rabbit disco plays in a background, and the chapter contains some of the hardest levels in the game.
Not So Harmless: At first, Dr. Fetus seems like a comical Jerkass villain whose worst crime is rather slapstick abuse of Bandage Girl. Then, at the end of the first world, he burns down the forest the earlier levels took place in For the Evulz and chases Meat Boy down in a giant saw robot powered by the blood of innocent woodland creatures, and it gets worse from there.
Oh Crap: Meat Boy's reaction when he has a bazooka in his face.
In 3-11X, one of the harder Salt Factory stages, it's possible to jump between or above the advancing buzzsaws so you don't have to go all the way to the right to jump over saws.
The Kid and Flywrench can become handy in some of the later chapter levels due to fact that in some levels, he can often skip the portions of the level entirely.
In the final boss level the sawblades advancing in front of you can be jumped over for additional speed. Oddly, if you get to your destination before the blades in that level, you become mysteriously immune to them.
Edmund McMillen claims to have been behind all this by purposely going on the PETA forums and trolling them with the game. They simply just took the bait.
Single Tear: Happens in the cutscene after beating the first boss.
Smash to Black: Right before Brownie appears in the ending.
Listen to it here. Happy music, worst forty levels of your entire life.
Spikes of Doom: Although they're replaced by syringes, salt and so on in most of the levels, genuine ones appear in some of the warp zone levels. In the Hell and The End chapters, some very sharp spikes are encountered.
Stealth Pun: Our hero is a skinless boy, who looks like a block of beef. Who frequently dies. Dead meat.
The character select screen is a Shout Out to Super Mario Bros. 2, complete with the spotlight and curtains. The curtains are made of flesh as well. Meat curtains.
Sting: Enter chapter: Dun! Dun! DUNNN! It also happens during the good ending.
It's also the sting used in the Dramatic Chipmunk video.
Why Don't You Just Shoot Him?: Dr. Fetus finally shoots Meat Boy three times with a rocket launcher in the last level. He respawns three times, just like he does whenever he get shot, cut, or otherwise killed.
To drive this home even further, in Cotton Alley, where you play as Bandage Girl and you have to save Meat Boy, whenever Dr. Fetus shows up to disrupt your reunion, he never beats Meat Boy up before abducting him.