Dynamite Headdy is a Platform Game by Treasure with the unique feature of taking place in and behind the scenes of a puppet show. You control Headdy, a puppet with a detachable head that can be used as a projectile, on a mission to confront Dark Demon, a Big Bad who has, quite literally, stolen the show. On your way you meet helpers such as Hangman, an animate handhold; Headcase, a walking box with a rotating selection of power-up heads inside; Beau, a visitor from Fluffy Cloud Heaven who points out bosses' weak points; and Heather, a mysterious woman with detachable hands.The puppet show nature of the game's setting comes up quite a bit, although it also has elements of a live action play or a movie. Each stage of the game is called an Act, and is subdivided into sections called Scenes. Backgrounds are often missing sections through which the backstage area can be seen, and sometimes actually fall apart. Some sections of the game take place backstage, and enemies and NPCs both sometimes take on the role of stagehands or other staff. Even the Life Meter reflects this: Headdy's vitality is represented by a klieg light whose color (and the size of the "H" in the middle) corresponds to the amount of life left, and bosses have a similar spotlight with an "E" in the center. There's also a scene where an orchestra is visible in the background playing the background music. Needless to say, metafictional and setting tropes get quite a workout in this game.
This game provides examples of:
2½D: Used in a few places, especially when rotation is involved, e.g. the tilting platforms in Act 3 Scene 1 and the boss of Act 5.
American Kirby Is Hardcore: Trouble Bruin in the original Japanese version was called Maruyama, was purple and had wide round eyes and a goofy smile. The USA version colored him brown and turned him into a Perpetual Frowner. Also, the USA game cover compared to the EU and JP ones.
Background Boss: Spinderella is a very notable example, as she can switch the camera's perspective to make it so Headdy is in the background, and the camera faces her back.
Bait-and-Switch Boss: At the end of the second world it seems that Headdy is going against Trouble Bruin with one of his many weird contraptions, but as soon as he starts moving, Mad Dog, the real boss, falls from the sky and crushes Trouble Bruin, who gets stuck under Mad Dog for the entirety of the fight!
Beam Spam: Baby Face's third adult head fires a hemispherical spray of lasers followed by a longer beam aimed at Headdy's position related to Baby Face in a very fast alternating pattern.
Bonus Boss: After the end credits have finished rolling, a numerical keypad appears. Entering the correct randomly-generated four-digit password (whose digits you discover by beating the bonus game once per digit) allows you to fight an extremely difficult boss. Fortunately, against this boss you have infinite lives.
Bonus Stage: Most stages have one Liberty Head, which leads to an "intermission" Mini-Game where machines spit out a continuous stream of basketballs (and the occasional bomb) and you must knock them into the two moving tiers of hoops above. There are three special hoops that do something different from awarding you a point if you dunk a basketball in them: a hoop with a basketball symbol that doubles the rate of basketball fire, a hoop with a "slow play" symbol that reduces the speed at which the hoops move, and a hoop with a Keymaster symbol that destroys one of the ball machines. There is no time limit for getting the requisite score to win; you lose by getting hit by too many bombs, getting both machines destroyed, or forfeiting by canceling the head. The reward for completing the bonus game is one digit of a four-digit password to be used at the end of game after the credits roll. With each digit you get, the number of baskets you need to make increases by five (from a starting value of five) and the frequency of bombs increases slightly. Once you have gotten all four digits, the Liberty Head icon will no longer appear on Headcase. One perk of entering the bonus game is that when you leave, whether you win or lose, your health is returned to maximum.
Bonus Stage Collectables: The four digits collected in the intermission bonus games are used to open the door to a Bonus Boss at the end of the game. There are seven chances total.
Broken Record: Beau's Training Stage has her say "Target!" every time an enemy is about to pop up, which becomes increasingly frequent over time.
Butt Monkey: Bino, classified by the game as a backstage worker, appears often "on stage" in many ways (grabbed or thrown in by a boss, boss wearing a MASK of him, wandering aimlessly on the arena...) and his elimination is the key to get many of the Secret Bonus Points. So albinos get the shaft again, but hey, at least he's not evil.
Chain Reaction Destruction: Bosses, minibosses and some pieces of scenery seem to have invisible explosive charges planted on them which activate when the object they're attached to, is damaged enough.
Chickification: Heather appears to be an Action Girl at first, going as far as to defeat one of the Keymasters before Headdy shows up, but later on in the game, she gets captured and must be rescued. Twice.
Some may say that she deserves a break for some of this: The first time she was blindsided by That One Boss, who showed up out of frickin' nowhere, and the Japanese version explains the second one: She was trying to reach out to Smiley, and he attacked her in response. Still though...
Climax Boss: the end-of-act bosses are Keymasters (well, at least from act 2 through 6), but Nasty Gatekeeper (end of act 7) is certainly one. If the Keymasters count, Twin Freaks (end of Act 8) does too.
Cultural Translation: There are several, the Level names in western releases are parodies of Movie/Music names while in the Japanese version, they just give the general level idea in a simple phrase. The Geisha in Scene 7 is replaced by a robot who is far less threatening when they change forms as the original had sharper claws than the robot. In stage 4 of the Japanese version Mons Meg was a large doll named Rebecca. Maruyama was changed from Purple to Brown in the western version. The Heavy head's icon was changed from the japanese characters to a large onion of some type. Even the ending has some minor differences. In the Japanese version, Smiley latches onto Headdy's head and he tries pulling it off humorously, while in the Western releases Heather hugs Headdy, though this may be because there was no dialogue in the Western release.
Cutscene Incompetence: The Robo-Collector captures Headdy at the start but is no threat at all during gameplay. Also a rare unintentional example: Headdy jumps on the first few steps of the tower level on his own, but about 1 in 10 times, the programming omits something and he falls off, causing minor damage.
Deflector Shields: Protector Head surrounds Headdy with a ring of fireballs that damage enemies. Not impenetrable, but nothing's getting in without taking a hit first.
Didn't Need Those Anyway: The Dresser and Baby Face, in different ways. Dresser is vulnerable after losing everything, but quickly brings in new stuff afterwards. Baby Face slowly loses faces until he runs out.
Difficulty By Region: The game starts with 3 continues in the Japanese version but none in the North American/European version (you can earn continues in both versions) and has a few other tweaks to make the American/European version more difficult. On the other hand, Twin Freaks, one of the hardest bosses in the game, has twice as much health in the Japanese version, but you can cheat against it, which is impossible in the other version.
Frickin' Laser Beams: Rocket Head fires lasers straight forward. Can penetrate certain barriers that the other shmup heads' projectiles cannot.
Guide Dang It: Many of the Secret Bonus Points require you to perform extremely counterintuitive or un-obvious actions, and there are no hints anywhere. Fortunately, they're not mandatory, and in fact, aren't worth a thing.
Heal Thyself: Sleepy Head. Headdy goes to sleep and gradually regains health until he is fully revitalized. Can be dangerous to use if you're currently under attack, although it can be canceled like most heads. There is also a non-head healing item, the Jelly Bean, which restores half of your maximum health.
Hitbox Dissonance: Used deliberately. Headdy's body can take damage while his head cannot, whether or not it is attached to his body. This becomes important at some points. The key to beating a certain boss is noticing that it targets Headdy's head instead of his body. It also means that ducking is not very useful for dodging damage, as due to Headdy's proportions most things that can hit him while he is standing will still hit him when he is ducking. The solution is generally to don the Pin Head, making Headdy's body small enough that hazards go over it. Ducking is still useful for hitting low targets, though.
Hold the Line: The penultimate level has Maruyama's robot go out of control and chase both of you down a very long hallway. The robot is invincible, and Maruyama himself may only be stunned. Maruyama spends the whole sequence tackling and clinging on to you because he needs somebody to hug during the stressful experience, while you desperately Try Not to Die. For about four minutes.
Homing Projectile: Pig Head fires two of them from its nose, but unlike most heads cannot be fired itself. Good for dealing with enemies from a distance, but not for much else.
Hostile Show Takeover: The event that kicks off the plot, with Dark Demon forcibly derailing the puppet show from whatever it was originally going to be about. Also referenced in the Japanese version before the fight with Maruyama in Act 3, Scene 2, which helps explain his motive:
Maruyama: Let's begin the next scene right now! It's time for Dynamite Maruyama's entrance!
Improbably Female Cast: Partially. The main character and a few enemies\supports are male, but most enemies and bosses are female (a little more obvious in the Japanese version). Of course, in this case, there's no Fanservice element to this... hopefully.
Incredible Shrinking Man: Pin Head, which makes Headdy tiny. Useful for getting through small openings and avoiding certain hazards. When it shows up you usually face a fork in the road with a tiny path where you need Pin Head to proceed and a normal-size path that often requires some other head. Even where the level layout doesn't actually split, Pin Head and whatever the alternative is will give you entirely different strategies for proceeding through the level. It's also useful to avoid an otherwise screen-filling fireball that Dark Demon likes to cheaply slide offscreen and shoot at you.
Intangible Man: Empty Head, which reduces Headdy to a white outline with no color inside. Rather one-sided, as you can still attack enemies but their attacks go right through you. Still vulnerable to Non-Lethal Bottomless Pits and damage from hitting Heather in the Nasty Gatekeeper fight.
Baby Face does it too in his last form (Grampa Face?). If his hand manages to grab you before you can finish him off, he makes a "Wah-wah-wah-waaaaah" noise, then appears to die of old age before exploding the usual way.
Made of Explodium: Most enemies. The explosion sound is high pitched and very unique. Speaking of unique, the way to get continues in this game: beat an end-stage boss, and they explode into a bunch of debris. Pick up most of the debris and you get a continue.
Mary Sue: Possibly invoked in the Japanese version, where it is revealed that Dark Demon was originally Smiley, an animate award that was supposed to be presented to the "greatest puppet", but instead interpreted this to mean that he was to become the greatest puppet, leading directly to his Start of Darkness and transformation into Dark Demon.
More Dakka: War Head continually fires projectiles in all directions, and Act 6's extremely bizarre Feather Head allows you to vomit a constant stream of tiny birds from your mouth as an attack. Also see Spread Shot.
Mutually Exclusive Power Ups: Aside from his normal head, there are over a dozen different heads Headdy can put on, each of which grants him a different special ability. Almost all of these can be switched for another head whenever you're near Headcase, revert to the normal head after a fixed time, can be canceled at any time, and revert to the normal head at the end of a Scene, but a few work differently: Pin Head lasts until the end of the Scene and can only be canceled by switching to another power-up; Head Trip expires after a time limit but can't be canceled and, since you can't shoot it, can't be switched; Bomb Head reverts as soon as it explodes; Liberty Head is really just the way you enter the bonus game; Air Head, Rocket Head, and Feather Head remain for the duration of Act 6 and cannot be canceled, although you can still switch between them.
Nintendo Hard: Some levels really test your ability not to smash the control through the screen.
No Fourth Wall: Played with, in that the characters are well aware that they're puppets in a puppet show, but aren't as obviously aware that they're characters in a video game.
At one point, while you're passing through a fairly normal area, Maruyama punches through the backdrop and drags you backstage.
This is also how he makes his entrance - By pushing the backdrop ONTO Headdy, signaling the first boss fight.
Non-Lethal Bottomless Pits: Falling off the screen doesn't kill Headdy, instead launching him back upward while damaging him some.
Oh, Crap: After what looks like a Breather Level in 7 you beat an easy boss then suddenly the background turns dark, revealing the enemy's castle, and the music lets you know That One Boss has arrived.
One-Hit KO: A cheat turns Headdy into this (though there is a glitch: in stark contrast to most side-scrollers, bottomless pits are the only thing in the game to not be lethal, even when the cheat is on). Without the cheat, nothing instantly kills Headdy for most of the game. Then the late-game introduces the concept of getting squished, and runs with it at the start of Act 9.
The Vacuum Head lets you do this to any enemy on-screen.
Poison Mushroom: Head Trip (known as the Buddha Head in Japan), a massive head made of metal which slows you down a lot and prevents you from jumping or shooting, and it makes strange faces too. It can't be canceled. It has a distressing tendency to show up during boss fights.
Power-Up Letdown: Vacuum Head is great for clearing away enemies and sucking up items but must be discarded if you need to do anything involving shooting your head to proceed, which is most of the time. Pig Head fires homing projectiles and is therefore similar to Vacuum Head but you can't get items either. Super Head's enhanced mobility will often send you flying into enemies or other hazards. Bomb Head makes you unable to do much of anything except avoid stuff while you're waiting for it to explode. War Head will sometimes lead to certain things being hit before you want them to.
Public Domain Soundtrack: The Nutcracker plays during the Mad Dog/Bouncy Boundy Boss fight complete with an orchestra and composer playing the music in the background.
Punny Name: The two puppets composing the puppeteer boss were originally named Marrio & Nettoh. (marionette)
Two Haniwa (those Japanese statues who are the basis for Cactuars in Final Fantasy) enemies were named Honeywan I and II.
Quad Damage: Slammer Head, which does twice as much damage per hit as the regular head.
Recurring Boss: Trouble Bruin, a bear (although he looks more like a cat, really) who also has a detachable head but instead uses it to control a wide variety of strange attack vehicles, Eggman-style. He is The Dragon to Big Bad Dark Demon.
This one's crafty; if you're standing on the ground, you can only see the "SHOOT" part of the block (but you still see the DON'T upon jumping, so it's certainly not obvious).
Schrödinger's Question: Inverted(?) with the PIN pad at the end of the game. Tool Assisted Speedrunners have determined that you can't guess the randomly-generated number; if you haven't collected all four numbers, you will always be wrong no matter what you punch in.
Scoring Points: The game has both regular points and Secret Bonus Points. Both do absolutely nothing and are only displayed at the end of an Act, so it's easy to forget they exist, save for the "500" point pickups that appear in some levels and the announcement when an SBP is earned.
"Gwahaha! That scene was a huge success! Regrettably, we haven't prepared the next scenario yet, but it'll be even more spectacular... ...maybe something like completely blowing up the puppet world!! Heady, my boy... I'll have you desperately fighting for your life again next time! Gahaha!"
Shoulders of Doom: Dark Demon has what appear to be green statues sprouting from the shoulders of his costume. Animated green statues.
Shout-Out: In addition to the many Sci-Fi-related puns the US version gave to level names (e.g. "Mad Mechs", "Terminate Her Too", etc.), the bosses are called Keymasters, and one of them as seen below is the Gatekeeper. Who ya gonna call?
Smart Bomb: Bomb Head, which doesn't harm you unless you're still wearing it when it goes off but does colossal damage to every enemy on the screen.
Sound Test: This and a button configuration are all there is in the options menu. Useful for players of the international version who want to hear the full versions of songs that only play during cutscenes and are cut short without the Japanese version's dialogue.
Spread Shot: Lotsa Heads fires three heads instead of one. Air Head is the approximate equivalent for Act 6, firing bullets in three directions at once. Air Head is also the only shmup head that allows you to face backwards.
Sprint Shoes: Super Head doubles Headdy's speed, as well as doubling his jump height and head-firing radius.
The Stinger: Played with in that it's a boss fight, not a cutscene.
Take That: The Japanese version has a secret ending that lashes out against Sequel Stagnation and Cash Cow Franchise: Headdy meets the creators of the game, who say they can't wait to make a sequel so they'll get more money by destroying Headdy's world even more! Headdy beats the crap out of them to ensure that there will never be a sequel and thus his world will be eternally safe. This is also a bit of a meta-reference, since Treasure are notoriously averse to sequels.
Theme Naming: Headdy has a detachable head. Fingy (Heather in the English version) has detachable fingers.
Time Stands Still: The Ticker Head freezes everything except Headdy for about eight seconds.
Toy Time: Due to the nature of the game's setting, all areas have a little bit of this, if only in the enemies (the Keymasters are so named because they are giant wind-up toys, and plenty of Mooks have smaller keys), but the toy theme is especially strong in Act 2.
The Unfought: Heather beats one of the bosses for you; you never get to fight or even see her. Trouble Bruin also has a machine that you never fight because a Keymaster falls on it.
Unique Enemy: When you see one, there's a high chance you get a Secret Bonus Point for killing it.
Unwinnable by Mistake: If you're on the top-right corner of the screen after Baby Face, and you skip the tally screens as fast as possible, Headdy will not have enough time to go to his spot, and will stop midway, locking the game. You can also kill Clothes Encounters off-screen by landing the final blow with the Super Head. This would almost make the game unwinnable, if it weren't for the fact that, around 4 minutes later, everything returns to normal. Videos here: 
Use Your Head: For combat, picking up objects, grabbing ledges, climbing walls, operating machinery, flying...pretty much everything that's not walking and jumping, really.
Violation of Common Sense \ Heart Is an Awesome Power: Pin Head, the head that makes you tiny and decreases your firing radius, walking speed, and jump height accordingly, and usually leads to the safer, less rewarding path in the early game, but in a level near the end, it leads to a challenging path that ends with the only 2-up reward in the game, and it is very important against final boss.
Warmup Boss: The first fight with Trouble Bruin, especially in the Japanese version where the balls of light don't do damage, though he's not a danger in the NA version either given he has 2 HP and you will have at least 14. Mad Dog, the boss of Act 2, probably counts as well; he has more health and a variety of attacks, but compared to the rest of the game, still a cakewalk, especially with all the goodies Headcase brings to the fight.
Long Song, Short Scene: Trouble Bruin's / Maruyama's theme plays when he enters a scene. In the Japanese version, it continues to play during the storyline, but in the other version, there is no storyline, so the only way to hear it in full is through the sound test. The song uses a couple of voice samples that aren't anywhere else in the game. Also the music that plays when Dark Demon's castle is revealed, which is similarly cut short in the international version.
Wall Crawl: Spike Head grabs onto any surface as if it is Hangman and pulls Headdy's body along with it. The body doesn't stay there, though; it falls back down once it's been pulled. Repeated shots allow you to climb walls or cling to ceilings.
Weapons That Suck: The Vacuum Head sucks in any items and enemies on the screen. It cannot be fired, though.
Widget Series: It's a game set in a puppet show, starring a puppet with a detachable head. The Widgetiness is especially high in the Japanese version, which contains robot kabuki performers, a gigantic doll firing Eye Beams, a bright purple Trouble Bruin with a fixed grin (referred to as Maruyama), and bizarre dialogue.
Your Head A Splode: What happens when you die. Also used to your advantage with Bomb Head.
Zero-Effort Boss: You can't lose to the last stage of Baby Face, the old man. If he does catch you... he dies of old age without doing any damage at all to you, and you win the fight. The only reason to try to avoid the hand is to earn the Secret Bonus Point that appears if you deal enough damage to the old man head.