[[quoteright:320:http://static.tvtropes.org/pmwiki/pub/images/keen4title.gif]]
[[caption-width-right:320:Let's see here... if I manage to complete my epic planet-spanning mission in four hours or so, I'll be back home just in time for supper.]]

A series of video games developed at the turn of the 90s, one of the first to be successful at replicating the side-scrolling action of the {{NES}} ''SuperMarioBros'' games in {{MS-DOS}} (more on that down below). The cartoon-style platformers are notable for their pioneering use of EGA graphics and shareware distribution, and because they were some of the first games by IdSoftware (which went on to develop blockbusters like ''VideoGame/{{Doom}}'' and ''[[VideoGame/QuakeI Quake]]''). Although developed by id, most of the Commander Keen games were published by Apogee Software, an already established MS-DOS shareware game publisher.

Billy Blaze is an 8-year-old boy genius who has constructed a spaceship in his backyard from old soup cans and other household objects, called The Bean-with-Bacon Megarocket. When his parents are out and the babysitter falls asleep, he dons his brother's Packers helmet and becomes Commander Keen, Defender of Earth.

The games' development began while the team that would become id Software worked at Softdisk, creating small, rushed games as a special division called ''Gamer's Edge''. John Carmack had perfected a technique for displaying smooth scrolling graphics on the PC, once thought to be possible only on consoles. Using this code, Carmack and Tom Hall took the protagonist from one of coworker John Romero's games, ''Dangerous Dave'', stuck the character in a recreation of the first level of ''SuperMarioBros 3'', and called it ''[[http://www.youtube.com/watch?v=cj4HJkeQSg0 Dangerous Dave in Copyright Infringement]]''. The demo was put on a disk labeled "Run Me" and left on Romero's desk as a practical joke. He was glued to the "prank" for hours, and knew they could make a game of their own with Carmack's code. Tom Hall suggested a game about an 8-year-old kid who saves the universe, shareware publisher Apogee told them they would distribute it, and the rest is history.

The series comprises several installments:

* ''Marooned On Mars'' (1990): The first part of the ''Invasion of the Vorticons'' trilogy. While exploring Mars, Keen discovers that the Vorticons have stolen four key components from his ship, and must journey across the landscape to several cities to retrieve his equipment. Featured the first appearance of Keen's signature pogo stick.
* ''The Earth Explodes'' (1990): Keen makes it back to Earth, only to discover that the Vorticon mothership is in orbit, and is planning to fire on eight key cities across the planet. Keen must board the ship to disable each of the eight X-14 Tantalus Ray cannons before they fire. The game featured a DarkerAndEdgier aesthetic; everything attacked Keen immediately, and there were many more pitfalls and dangerous objects to avoid.
* ''Keen Must Die!!'' (1990): The final part of the ''Vorticon'' trilogy. After disabling the Vorticon mothership, Keen travels to their home planet in search of the mysterious force that had directed them to Earth. The game featured various Vorticon cities and establishments, and allowed players to learn the Galactic alphabet (a heavily-advertised feature that allowed players to go back to the previous installments and decipher various signs in the levels).
* ''Keen Dreams'' (1991): A GaidenGame published by Softdisk, where Keen has a dream in which he sets out to fight Boobus Tuber, the vegetable king. The game's canon status is unknown - most fans consider it to have taken place between episodes 3 and 4. The game featured several features unique to the series, including a lack of Keen's pogo stick, and vegetables being thrown as weapons.
* ''Secret of the Oracle'' (1991): The first part of the ''Goodbye, Galaxy!'' two-parter. After finishing a new sublight radio, Keen discovers a plot by a new alien race, the Shikadi, to take over the galaxy. He travels to the planet Gnosticus IV to consult the Keepers of the Oracle (an ancient alien race), but discovers they have been captured, and sets out to rescue them. The game featured much larger levels and a wide assortment of enemies, as well as new game mechanics and minigames.
* ''The Armageddon Machine'' (1991): The final part of ''Goodbye, Galaxy!'' Keen lands on a massive space station called the Omegamatic, manned by the Shikadi, and sets out to deactivate the machine and save the galaxy.
* ''Aliens Ate My Babysitter!'' (1992): Keen's babysitter Molly is kidnapped by an alien race named the Bloogs, and he must rescue her by fighting his way through the planet Fribbulus Xax. The game was published by [=FormGen=] and resold by Apogee (See KeepCirculatingTheTapes below).
* ''Commander Keen'' (2001): A GameBoy Color title published by Activision.

Though ''Aliens Ate My Babysitter!'' claimed that a third trilogy titled ''The Universe Is Toast!'' would be released in Christmas of 1992 (via its ending credits), it never saw the light of day. Id moved on to bigger and better things, and eventually declared the series dead. However, Tom Hall (no longer with id) has promised to continue Keen's story if he can acquire the rights. Additionally, a FanSequel ''The Universe Is Toast!'' trilogy has been released, made from heavily modded versions of episodes 4-6. Fan reactions have been overwhelmingly positive.

Tom Hall has announced a GameMaker titled ''Worlds of Wander'', which will include a SpiritualSuccessor game to ''Commander Keen'' titled ''Secret Spaceship Club''. Its Kickstarter campaign failed; however, Tom has said the team intends to work on it in their spare time anyway.

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!!This game series has examples of:
* AcmeProducts: Acme blueprints in ''Earth Explodes'' and ''Secret of the Oracle''.
* AmazingTechnicolorPopulation: Due to EGA graphic limitations, all humans are completely white-skinned. As in WHITE-white. Princess Lindsey is also black (a realistic dark-skinned shade, as opposed to #000000), if human-featured fairies can be considered human.
* ApocalypseHow: ''Earth Explodes'' has the villains of the first episode position a planetary destruction ship in orbit over Earth. If you screw up, you get to activate it. [[ExactlyWhatItSaysOnTheTin Guess what happens]].
** If you get a game over in Episode 5, you are rewarded with a scene of the galaxy blowing up as [[SoundtrackDissonance happy music plays in the background]].
* BadassGrandpa / BadassFamily: According to the VideoGame/Wolfenstein3D hint manual, William Blazkowicz has a grandson by the name of B. Blaze. Furthermore, the Cyberdemon encountered at the end of Doom is missing an arm and a leg. The same ones that William cut off the oddly-familiar Harbinger in Wolfenstein RPG. You know, the demon who vowed [[CycleOfRevenge revenge]] on William's descendants? Might Doomguy be Billy's decendant? In any case, even without Doomguy, Billy Blaze has a pretty badass family.
* BatmanCanBreatheInSpace: Commander Keen and the Vorticon Guards have no problem breathing on the surface of Mars.
* BigEater: Nearly all of the items are [[SweetTooth candy]], food or soda. Keen sure loves his junk food.
* BilingualBonus: Though in this case, the language is a "space cypher" used throughout the games.
* BlackoutBasement: In episode 2 Keen can switch off (and back on) the lights in some levels. This is helpful; "A wise Vorticon never jumps in the dark. In fact, even unwise Vorticons will not jump in darkness."
* BondVillainStupidity: [[LampshadeHanging Lampshaded]]. Keen is surprised that the Gnostic Elders weren't killed instead of just being kidnapped. The council page immediately handwaves this by telling him that the elders are immortal. (Which also excuses for preventing the player accidentally - [[ForTheEvulz or not so accidentally]] - killing them.)
* BonusDungeon: Most games have several levels that are not required to be completed. For some, the means of accessing the level are secret and [[BrutalBonusLevel the difficulty level is significantly higher]].
* BossInMookClothing: Plenty of them, especially in earlier episodes: The Vorticon that guards the last ship part in the first episode, the Vorticon Elite in each of the Tantalus Ray levels of the second episode, the Vortimoms and Vortininjas in the third episode, and the Shikadis and their dog pets in the fifth episode.
* BoundAndGagged: Molly
* BreadEggsMilkSquick: The reason Keen doesn't like Mortimer [=McMire=] one bit is because the latter (a) taunted him, (b) gave him a wedgie, and (c) tried to destroy the Earth.
* BrutalBonusLevel: All of the secret levels are on the difficult side, as are most of the optional levels in [[NintendoHard ''Earth Explodes'']].
* TheBully: Mortimer, who enjoyed giving Billy swirlies.
* CanonDiscontinuity: Tom Hall's stance on the 2001 Game Boy Color game.
* CirclingBirdies: In games 4-6, any enemy stunned by Keen will have them. If you don't see any CirclingBirdies, that means the stunning will eventually wear off.
* ContinuityNod: Billy Blaze's full name is [[VideoGame/Wolfenstein3D William Joseph Blazkowicz]] II, after his grandfather, who you probably know better as "B.J.".
* CoolStarship: The Bean-With-Bacon Megarocket. It's made of ''soup cans'' and runs on [[strike:vodka]]''Everclear''. Admit it, you want one.
* CypherLanguage: The Standard Galactic Alphabet
* DistressedDamsel: Molly in ''Aliens Ate My Babysitter''.
* EarthShatteringKaboom: The threat in just about all the games.
** And in ''Earth Explodes'', [[WhatTheHellPlayer you can activate it yourself]]. Which ends your game, obviously.
* EveryTenThousandPoints: Or, rather, every 20000 points (in games 1-3) or every 10000* 2[[superscript:n]] points (in games 4-6.)
* EvilCounterpart: Mortimer [=McMire=], Keen's arch-nemesis, who constantly taunts Keen for having an IQ that's 1 point lower. He also looks quite similar, wearing a black helmet instead of a yellow one.
* FanSequel: While there have been several fan-made games and mods, one specific trilogy has been really well received and adopted as the unofficial "The Universe is Toast!" trilogy: [[http://www.shikadi.net/keenwiki/The_Keys_of_Krodacia The Keys of Krodacia]], [[http://www.shikadi.net/keenwiki/Dead_in_the_Desert Dead in the Desert]] and [[http://www.shikadi.net/keenwiki/Battle_of_the_Brains Battle of the Brains]], three mods of Keen 4-6 with new maps, enemies, and items.
* GettingCrapPastTheRadar: In the Paris Tantalus level in episode 2, there is a section with colored platforms that spell out - in SGA letters - a certain [[PrecisionFStrike expletive]]. However, it's actually misspelled "fucl" (intentionally, as explained by Tom Hall on his [[http://tomtomtom.wordpress.com/2011/12/14/happy-21st-birthday-commander-keen/ blog]]). This has become something of a MemeticMutation in the Keen community, with "fucl" (rhymes with "buckle") being a popular swear word on the forums.
* TheGoomba: Yorps in Commander Keen Episode 1, which can't damage you themselves. The only way they can kill you is to push you into something dangerous. A similarly harmless enemy in Episode 2, the Scrubs, can actually be helpful as they can be ridden upon to access areas you otherwise couldn't. (they can climb up walls). And the Bounders in episode IV serve a similar purpose.
* HintSystem: In the Game Boy version, arrows appear in the background to give players hints about the surroundings (because the screen is otherwise too small to see whether or not you can make a LeapOfFaith).
* IdleAnimation: Keen takes out a book to read and, in one level, moons the audience.
* ImprobablyHighIQ: And how, exactly, do you measure an IQ as high as 315. And how does ''anyone'' on Earth have an IQ of 314?
** [[DontExplainTheJoke Because Keen's IQ is a reference to pi, and [=McMire=]'s is one higher to show he's an elitist jerk.]]
* InfiniteOneUps: ''Commander Keen 2: The Earth Explodes'' has a rather {{egregious}} example in the Paris Tantalus level, where if you know how, you can get enough points to get more than one life each try, which can theoretically lead to infinite lives, not to mention infinite points. At least one level in ''3'' allows for the same abuse.
** In ''Marooned on Mars'', not only does the secret level allow this, but, since getting to it involves using a teleporter inside another level, you can loot the latter level, teleport out, make your way back on the world map, and repeat, allowing you to gain infinite lives (and ammo) without having to suicide
** The secret level in Commander Keen 5: The Armageddon Machine contains enough [[LawOfOneHundred Vitalin]] to gain two lives at the very start. Die, repeat...
* InsufferableGenius: Doesn't get much more insufferable than trying to kill everyone who is less intelligent than you.
* InterchangeableAntimatterKeys: Only in ''Keen Dreams''. In all the others, only ONE key will unlock a specific door.
* InvincibleMinorMinion: Every game had at least one. And some of them had invincible major minions as well.
* JumpPhysics: Keen is able to jump insanely high on his pogo stick. In ''Keen 4'', he gains the ability to pull himself up a ledge, which he previously couldn't.
* KeepCirculatingTheTapes: The full version of 6. [=FormGen=] actually published the title with Apogee reselling it as an retail product. Id like other Apogee developers kept the rights to the title. Id included it in the incredibly rare ''Id Anthology'' CD set. It's a ''little'' easier to find copies of that in order to buy ''Commander Keen 6'' (although it's still [[CrackIsCheaper a hundred bucks]]). Since Apogee/3D Realms sold their stock years ago, they don't have any further claim to the game. The rights to [=FormGen=]'s games seem to have been lost in the shuffle as each company went bankrupt and sold their intellectual properties to another.
* KidHero
* LawOfOneHundred - Rain Drops in 4, Vitalin in 5, and Viva in 6.
* LightningBruiser: The Gargs once they start chasing you. Seeing them jump chasms can be extremely disconcerting.
* MeaninglessLives, at least in 4-6, where the game save feature is essentially a built-in save-state system, and death sends you back to the start of the levels - meaning that SaveScumming is a way of life, which makes the lives useless.
* MiniDungeon: The Sand Yego castle in the fourth game. It's modeled after the pyramid levels, but it's shorter and less complex, and it can be skipped.
* MobileShrubbery: Commander Keen IV: The Secret of the Oracle has enemies that hide under boulders (much like the Toy Story 2 traffic cones). They're harmless (and well camouflaged) when stationary, but deadly when moving. And they can jump at you as if they're riding pogo sticks!
* MooksButNoBosses: Only three levels in the entire series have bosses: The final level in Episode 3 (Mortimer [=McMire=] on his Mangling Machine), Episode 5 (Shikadi Master), and Keen Dreams (Boobus Tubber). That said, there are various BossInMookClothing enemies in the series, as noted above.
* NintendoHard: The military installation levels in episode 3 (Fort Cavort, Fort Vorticon, Fort Vorta Bella, [[FanNickname Fort Vox]], and Cape Canavorta) are among the most difficult levels in the entire series. They're all optional, however.
* NoEnding: Beating ''The Armageddon Machine'' gives you a message saying "See you Christmas '92 when Commander Keen returns to battle for the universe! It'll be the biggest Keen ever!". Sadly, this grand finale was never made, and aside from a few fan-made {{Game Mod}}s, the series still ends on a cliffhanger.
* NonstandardGameOver: In the second game, there are Tantalus Ray Cannons you must destroy in order to save Earth. There are eight of them, but if you press a switch on the side of any of them, a Tantalus Ray shot will destroy the planet and your game is over instantly.
* NotQuiteDead: The Arachnut and Blue Birds from Keen IV can be temporarily stunned if you shoot them with your ray gun, but never permanently killed. (Or permanently stunned. After all, the way other enemies "die" in the episodes IV - VI leaves them with stars going around their heads.) The first time you see them suddenly spring back to life is disconcerting, to say the least. (Incidentally, the gun you use in IV - VI is officially called a "neural stunner"; the background story to IV has Keen use it on his ''parents'', so it's definitely a StunGun.)
** The same goes for the Volte-face from ''Armageddon Machine''.
** Also, in ''Keen Dreams'', none of the enemies, except for Boobus Tuber, can be permanently killed. Keen can only temporarily turn them into flowers with the help of special bombs. On the other hand, if you flower-ize them when they're right next to a bottomless pit, they may fall off...
* OmnicidalManiac: Mortimer [=McMire=]. It's not that he wants to kill ''everybody,'' he just thinks that nobody dumber than him deserves to live. Of course, he's the smartest being in the universe...
* OneHitPointWonder
* OrphanedSeries: Although these games are a fairly enjoyable way to spend an afternoon if you're not busy, they were discontinued before a satisfactory conclusion could be reached, and a number of copyright hand-changes have made an official conclusion more or less defunct.
* PuzzleBoss: The Vorticon guarding the everclear in 1. As you're told by a Yorpish oracle, "You cannot kill the Vorticon Commander directly." [[spoiler:The solution is to shoot a cable, dropping a giant slab of stone on the Vorticon commander.]]
* RankedByIQ: Mortimer [=McMire=] brags that his IQ is [[ImprobablyHighIQ 315]], one point higher than our hero (which is 314 in tribute to Pi).
* SequelEscalation: The ''Invasion of the Vorticons'' trilogy had Keen fighting to save the Earth. In ''Goodbye Galaxy'', he saved the galaxy. The third trilogy, had it ever been made, would have had him up against a plot to destroy ''the entire universe''.
* {{Shareware}}
* ShoutOut: Several, the most notable ones being ToServeMan, ''VideoGame/Wolfenstein3D'' ([[ProductionForeshadowing which still had to be produced]]) and ''Franchise/TheHitchhikersGuideToTheGalaxy'' (the Dopefish is the second dumbest creature in the universe, after all...)
* SocialDarwinist: Mortimer [=McMire=]. He thinks everybody dumber than him (which is everybody in the universe) deserves to die.
* SpikesOfDoom
* StealthPun: In order to get to a secret level in Episode 4, one must collect 12 worms together. This creates a giant foot that transports you. The fact that these must be "inch" worms is mentioned only in the help file, which even goes so far to say "Watch where you step or they'll be afoot!"
** Also the level-entry texts in the same episode; "Keen disappears into Miragia", "Keen backs into the Pyramid of the Moons", etc.
* StrangeSecretEntrance: The aptly-named "Pyramid of the Forbidden" in episode 4, reached by going into the basement of the "Pyramid of the Moons" and coercing twelve inch-worms to come together, at which point they form a [[StealthPun giant foot]] which transports Keen.
* StunGun: Your weapon in Episodes 4 through 6. Most enemies stay "stunned" forever, though--[[OffscreenInertia or at least until after you exit the level]].
* SuperDrowningSkills: In episode 4, you can't swim on the world map until you get the scuba gear (even though you stay above water). And in episode 3, pools of plain water kill you on contact.
* TemporaryPlatform
* ToServeMan: Given a coded ShoutOut in episode 6.
* UnreliableNarrator: If you read the story from the help file, you can come to the conclusion that the whole "adventure" is just in Billy's head - he's just playing in the garage and backyard.
* UnwinnableByDesign:
** Subverted in Episode 3: Keen Must Die! The "Impossible Maze of the Caves of Oblivion" before the final level is just that; if you face the challenge head-on and collect all the keycards hidden in the maze cave, you'll find that the level exit is right behind a gate of spikes with no way to get through them. What you're supposed to do instead is pogo up and over the mountain to a ''secret'' exit that's out in the open with no instant-death traps barring your way.
** It's possible to make Keen Dreams unwinnable if you complete every level in the game but don't collect at least 12 Boobus Bombs (the minimum number required to defeat Boobus Tuber). The game won't even let you enter the final level. Hope you have an earlier save...
** In Episode 4's Pyramid of the Gnosticene Ancients, you have to make sure you reach the key gem needed to exit the level before the item-stealing monster does.[[note]]If you have any lives left, you can suicide and thereby reset the level.[[/note]]
* UnwinnableByMistake:
** Due to level design goofs or glitches, in some cases it's possible to leave a level without having achieved the objective. For instance, in the "Cave of the Descendants" in episode 4, there's a door with no floor on the other side, so you fall if you walk through. Due to a glitch, you can, if you're fast enough, go back through the door before you fall, whereupon you instantly win the level. But now you can't rescue the elder from that level.
** On Episode 1, it is possible to exit the Vorticon Fortress level without collecting the Everclear (one of the 4 items needed to complete the game) by jumping over the Vorticon to reach the exit.
** If you play episode 5 on Easy difficulty, it's impossible to break the fuse in the secret level, and hence get the alternate ending; depending on which edition of the game you have, either it crashes as soon as you enter the secret level, or the fuse is simply unbreakable.
** Keen 6 is notorious for its glitches, some more serious than others. However, as [[http://www.youtube.com/watch?v=aEsUtMqcT8w&feature=relmfu this]] playthrough by ReedWulf demonstrates, it is possible for a crucial item (blue key) to drop through the killer trap and off the map ''in the last level'', making the game unwinnable by... malice?
* VisualPun: If Keen stands on one of the crescent moon symbols in the Pyramid of the Moons, and left idle, his first IdleAnimation is to [[{{Mooning}} moon]] the viewer. In episodes 4-6, the doors are opened by using the matching colour gemstone -- key stones.[[note]]Is this what's known as "arch" humour?[[/note]]
* YourPrincessIsInAnotherCastle: the janitor at the end of the Pyramid of the Forbidden.
* TheWallsHaveEyes: ''6'' has a few eyes on the background of some stages, and the final stage involves a part where you have to use giant eyes hanging from the roof by their optic nerves as platforms.
* {{Wingdinglish}}: The Standard Galactic Alphabet. A standard substitution cypher, you can look at the conversion table [[http://www.google.com/imgres?imgurl=http://www.3drealms.com/keenhistory/sga.gif&imgrefurl=http://www.3drealms.com/keenhistory/keenhistory3.html&usg=__eNtSGwd9DXysgTCNkTNDd_llXF0=&h=646&w=800&sz=218&hl=en&start=5&zoom=1&itbs=1&tbnid=rGlCnCrRAZ_EuM:&tbnh=115&tbnw=143&prev=/images%3Fq%3Dstandard%2Bgalactic%2Balphabet%26hl%3Den%26client%3Dfirefox-a%26hs%3Dn6N%26sa%3DX%26rls%3Dorg.mozilla:en-US:official%26tbs%3Disch:1%26prmd%3Divns&ei=NotlTeuSEYL48AaDvdWPBw here]].
* WritingAroundTrademarks: The game originally started as a ''VideoGame/SuperMarioBros'' clone for [=PCs=]. id tried to get Nintendo to distribute it, but they weren't interested, so they used the engine to create an original game.

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