Bloons Tower Defense / Tropes D to I

Bloons Tower Defense Trope Examples
A - C | D - I | J - M | N - R | S - Z

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D

• Damage-Increasing Debuff: Some debuffs allow towers to pop additional layers to affected Bloons, or just deal multiple damage to MOAB-class bloons. This type of damage is especially potent since it affects every hit of every projectile, and it's one of the few types of debuffs that can affect the BAD.
  • Embrittlement is a tier 4 upgrade for the Ice Monkey in BTD6. Bloons frozen by this monkey will pop an additional layer when attacked, but it can't freeze MOABs (though as of 28.0 it will apply the damage debuff). The tier 5 upgrade Super Brittle allows the tower to target MOABs, as well as increasing the damage to four extra damage instead of one.
  • The BTD6 version of Sniper Monkey's Cripple MOAB upgrade allows it to not only stun blimps, but also increase the damage it takes by five. Against a BAD, the stun is ineffective but the damage increase still applies.
  • The 9.0 patch of BTD6 gave Glue Storm this ability. When the ability is activated, all glued bloons on the screen take an extra layer of damage.
  • These are extra important against the Lych boss bloon, as its mechanics mean that traditional temporary buffs like the top path Alchemist and Overclock are more of a liability than a benefit.
• Damn You, Muscle Memory!: An infrequent example of something not related to controls but rather gameplay; in BTD6, Hard mode actually starts you on round 3 instead of 1. Likewise, Impoppable and CHIMPS start you on round 6. This means that you have even less time to get extra cash!
• Deadpan Snarker: The pre-round comments in these games are occasionally rather snarky, if not outright menacing.
  BTD1, round 49: Its ok if you don't pass this level. Really it is. Just hit 'try again'. Its the effort that counts.
  BTD5, round 76: Next level will be fun, a whole bunch of Ceramic Bloons are going to charge through your defenses and pretty much make you lose.
  BTD5, Impoppable round 85: Next up is the final round, beat it and you'll gain the Impoppable medal. You won't though, this has been a waste of time and you won't survive what's coming. At least you had fun.
  BTD6, alternate round 6: Did you panic when you saw the Camo?
  BTD6, alternate round 9: Hmm, wonder when will the first Lead will appear?
• Degraded Boss:
  • MOAB-class bloons are introduced in a boss-like fashion (facing one of them alone in the level they are introduced), but they quickly become regular bloons afterwards, up to the Freeplay levels, in which everything eventually spawns as the strongest MOAB-class bloon available.
  • Downplayed with the BAD in the sixth game. It first appears on round 100, but sparingly appears after that in Freeplay rounds as special encounters. You'll never be Zerg Rushed with BADs as opposed to, say, the huge stack of ZOMGs that appear two rounds before the BAD's first appearance (or the horde of 30 DDTs three rounds before that).
• Depth Perplexion:
  • Presumably, the bloons are floating above the track, yet they are affected by spikes lying on the ground. And the Monkey Ace is flying even higher above them, yet its darts can pierce through bloons as if they were on the same level.
  • Taken a step further with the obstructions in BTD6. On some stages, towers will not be able to "see" past these obstructions if you place them in specific locations, meaning that they can't pop whatever's behind them, although some maps (such as Tree Stump) feature another level in which you don't have obstructions, which creates this as any projectiles should be higher or lower depending on where they're placed, yet still manage to pop the bloons.
  • The Heli Pilot's Razor Rotors upgrade uses the helicopter blades to shred Bloons, even though the helicopter is flying above the Bloons.
  • A mod that allows you to move the camera shows just how much more of this trope applies, most of which are hidden by the Fixed Camera angle. The projectiles' models don't even need to physically touch the Bloons' models to damage them.
• Developer's Foresight:
  • Churchill in BTD6 can utter "Protect that exit!" whenever the Bloons start to leak. In maps with multiple exits, this is changed to "Protect those exits!"
  • On Alternate Bloon Rounds, depending on if you have lost any lives or not by the end of round 7, there may be a comment asking if you are still on max lives, and it will only appear if you haven't lost any lives.
• Difficult, but Awesome: Regrow farming, the specific strategy of exploiting the fact that you can make rounds last forever by pushing back regrow bloons, letting them regenerate, then pushing them back again, giving infinite time to activate cash producing abilities. However, this comes at the risk of the regrowing bloons multiplying to the point where your defenses are overwhelmed.
• Difficulty by Acceleration: From Round 80 onwards, all bloons start moving faster (and tougher, in the case of MOAB-class bloons) with each passing round. They start moving even faster once you reach Round 110, where the round speed increase becomes higher.
• Disc-One Nuke:
  • Monkey Subs have been considered a Disc-One Nuke ever since their introduction in the fifth generation of the franchise, due to their power for a player's buck. For instance, their Airburst Darts cost approximately $1000 but quadruples the projectiles fired at the bloons, and Twin Guns allows them to fire twice as fast for less than $500. (In comparison, comparable buffs for other towers cost thousands of dollars.) They also have an upgrade, Advanced Intel, that lets the subs use the targeting range of any other tower already placed on the map, and can also absorb the camo detection of other towers for merely $540. In Bloons TD 6 in particular, they can be buffed by alchemists to double their damage and add even more anti-blimp damage as well as lead popping capabilities, making submarines the go-to for Half Cash mode.
  • Berserker Brew and Stronger Stimulant, top path alchemist upgrades, essentially turn other towers into Disc One Nukes. These allow the alchemist to buff other towers' damage output significantly. These buffs include pierce, damage, range, and attack speed simultaneously and stacks with the Acidic Mixture Dip upgrade in the same path to provide extra lead, ceramic and blimp popping power. Stronger Stimulant in particular allows the alchemist to buff two other towers (or three with the Faster Throwing crosspath). Particular towers that these alchemists easily turn into Disc One Nukes include Bloonjitsu, bottom path Tack Shooters, Spiked Balls, and Monkey Subs. Their status as this is defied when facing the Lych boss bloon, however, which eats temporary buffs to heal itself.
  • Recursive Cluster qualifies due to it being a Jack of All Trades for around $6000. It pops all bloon types, deals colossal area-of-effect damage to ordinary bloons, and at the same time does decent against low-level blimps.
  • Spiked Balls is yet another example. It pops all bloon types, at least doubles each spike pile's damage (quintuple against ceramics), and increases their pierce by 40%, and costs only around $6000 total. Berserker Brew adds even more damage and pierce. It will eat virtually every early-game bloon for breakfast, and will eat early MOABs for lunch too. Unlike many another examples of this trope, Spiked Balls also have Magikarp Power later on against Super Ceramics.
  • Sauda is a hero designed to be a Disc-One Nuke. She can be placed on the first round of almost any game mode (except Impoppable without Monkey Knowledge), always detects camo, and does a great job keeping pace with early-game rushes of low-level bloons due to her swift, moderate-pierce sword slashes. With Alchemist buffs, she can also keep up with early rainbow and ceramic rushes. As an added bonus, her level 3 ability instantly wipes out the ceramics spawned by the Round 40 MOAB.
  • Before it was nerfed in 34.0, Wall of Fire was notorious for being able to defeat most rushes weaker than a ceramic by itself, despite merely being a tier 2 upgrade costing $1000. Even after the nerf, its succeeding tier 3 upgrade Dragon's Breath retains the un-nerfed wall of fire attack and itself is pretty cheap (only $3000!).
• Do Not Touch the Funnel Cloud:
  • The Monkey Apprentice's tornado magic can blow quite a few bloons back, but it only affects the ones it touches directly. The winds are, however, strong enough to remove ice and glue from blown bloons. Be careful when using wizards with the tornado upgrades in levels with regrowth bloons; if these bloons are not popped quickly upon being blown back, the will regrow into massive armies that rush past your defense.
  • In BTD6 the Druid gains this ability instead, and its final upgrade, Superstorm, can even blow back MOAB-class Bloons!
• Doomy Dooms of Doom:
  • One of the Daily Challenges for BTD5 was called Rainbow Rush of Doom.
  • The Ray of Doom, a fourth/fifth-tier upgrade^note  Fourth tier in BTD5, fifth in BTD6 for the Dartling Gun, which can destroy any and all non-ZOMG bloons in seconds.
  • Bloons TD 6 introduces the Big Airship of Doom. It has the second-highest HP count of any bloon introduced in the main series (the only bloons with more HP are the "Test Bloon" you can only find in Sandbox and the higher tier Boss Bloons in their events), and is immune to any slowdown or knockback effects that affect other MOAB-class bloons.
• Double Unlock: In BTD5, you unlock a weapon's upgrade path via having a high enough rank, and the tower class needs to be at a high enough level.
• Dread Zeppelin: The most powerful bloons are the MOAB-class bloons, huge and often slow blimps that take a lot of damage just to pop their first layer.
• Dwindling Party: In Odyssey Mode, you can only take certain number of towers with you to complete a series of maps. In Extreme Odyssey Mode, the non-hero towers you use in one map will be unusable in the next.

E

• Early Game Hell:
  • TD 6's Alternate Bloons Rounds mutator for Hard Mode has this in spades. The premise of the mode is that more powerful than usual Bloons will spawn in each round. This means that the early game will be frought with lead and camo Bloons that you'll be hard pressed to have towers even capable of popping without resorting to powers or instamonkeys. Once you reach wave 20 or so, it's not much more difficult than regular Hard Mode.
  • The Apopalypse game mode also has a case of this, because you don't get any end-of-round cash bonus, which usually is a large portion of your income early on. However, once you've reached midgame, you get enough cash from popping Bloons and/or farming such that the lack of the bonus becomes insignificant.
  • In general, the way harder maps are designed tends to more heavily up the challenge of the early game than the late game. Harder maps prefer to use multiple pathways and undeployable terrain to spread the player's towers thin over a large play area. Late game, the player has enough money and towers to meet the needs of several pathways at once, but the early rounds require fending off several waves of bloons with only a few dart monkeys or tack shooters, and it will be a while before mapwide covering towers like Mortars or Helicopters become reasonable to buy.
• Early-Installment Weirdness: The fourth game introduces Camo Bloons. However, in this game, the Camo Bloon is a specific type of bloon, rather than a property that any bloon can have like in the following ones. Additionally, Camo Bloons can be affected by collateral or splash damage from any tower, while in the next games, they completely ignore attacks from towers that don't have camo detection.
• Easter Egg:
  • You may not want to tap BTD6's heroes too much in a short period of time... Gwendolin sums it up as well.
    "I wouldn't do that if I were you."
  • However, you may want to try tapping the buildings on the menu screen; you may see a few monkeys pop up!
  • Another nice attention to detail is that the village clock on both the menu and in gameplay match your system clock.
  • On the map Candy Falls in BTD6, there are clickable spots that cause an Oompa Loompa monkey to run around. Clicking them in the right order makes the Oompa Loompa song, and also unlocks Small Towers.
  • If you summon the True Sun God while Adora is at max level, she will get a buff that makes her attacks three times stronger. Her visuals also change. She has a different pose, her eyes glow, and she gets an elaborate headdress in the shape of the sun.
    If you summon the Vengeful True Sun God, on the other hand, Adora will transform into a red and black version of herself. If you do this while in Adora's Temple, the entire map will grow darker and the temple itself will also change into red and black. On Lotus Island, the VTSG will turn the lotus pollen bombs into purple.
  • In the map Frozen Over in BTD6, there's a caveman monkey frozen inside the ice. Previously it was just a decoration, but in later updates, you can free it as a secret tower, referencing memes about freeing the monkey. You need to target the block he's frozen in with Mortars. Once freed, the Cave Monkey will be placed randomly on the map. His damage is weak, but he can stun anything except a BAD.
• Easy-Mode Mockery:
  • In a visual example, the picture for easy mode in BTD4 onwards is a baby monkey.
  • Subverted on Extreme difficulty tracks on BTD5. The Easy mode is merely a Point Five Oh Sniper Monkey, the Medium being a Ray of Doom Monkey, and the Hard mode is a Sun God Monkey. You know it's Extreme when the easy mode pic is a badass (although not as badass as the other two).
• Elite Mooks: Ceramic Bloons, the strongest of the regular Bloons. Unlike weaker Bloons, which can only take one hit before popping, a Ceramic Bloon can take 10 hits before popping into Rainbows. In addition to having multiple hitpoints, Ceramic Bloons are also fast, being the fourth-fastest regular Bloon type, just below Pinks, Yellows, and Purples. Past round 80, Ceramics are replaced by Super Ceramics, which have a whopping 60 HP in exchange for only leaving a single descendant when popped.
• Excuse Plot: The tutorial of BTD6 has the plot of protecting a town from a Bloon attack. That's about the only thing resembling a plot in the game. No other reasons are given as to why monkeys are popping Bloons in the grassfields, in tropical island, on the moon, and other tracks.
• Exactly What It Says on the Tin:
  • The Beginner-level map "Three Times (3x) Around" in BTD5, in which bloons circle the central loop, well, three times. This gives your towers two additional chances to catch bloons, but heavier bloon overlap makes it more difficult to know if bloons are about to escape.
  • In BTD6 we get Four Circles, which is a track comprised of four circles that the Bloons go around before exiting. To give it a bit more flavor, it's styled after a track-and-field course.
• Eye Beams: The Super Monkey uses these as upgrades. First it uses lasers, then plasma, and then sun rays.

F

• Fanboy: One of the final upgrades for the Dart Monkey turns it into a Super Monkey Fan Club. It gives it the ability to turn itself and nearby Dart Monkeys into actual Super Monkeys for a few seconds. BTD6 has the Plasma Monkey Fan Club, which turns nearby Dart Monkeys into 2/0/0 Super Monkeys with increased pierce, attack speed, and damage instead of mere 0/0/0 Supers, and can also affect 20 Dart Monkeys instead of just 10.
• Floating Continent: The Floating Islands and Ascension tracks in BTD5 Deluxe feature these, but the islands in Ascension are Solid Clouds.
• Fun with Acronyms:
  • The games have a lot of them, notable examples being the names of the MOAB-class bloons.
    • The MOAB, also known as Massive Ornary Air Blimp. As for BFB, it's Brutal Floating Behemoth.
    • The ZOMG is the Zeppelin Of Mighty Gargantuanness.
    • The DDT stands for Dark Dirigible Titan.
    • The BAD from Bloons Tower Defence is the Big Airship of Doom.
  • One stage in BTD3 has the hint "MOAB stands for Massive Ornary Air Blimp, not Mother Of All Bloons. Either way, it brings pain."
  • From the fifth game's fandom comes NAPSFRILLS, which means No Agents, Premiums, Specialties, Farming, Road Items, Lives Lost or Selling.
    • The first three refer to the out-of-gameplay boosters like special agents, premium upgrades, and specialty buildings.
    • "No Farming" means no method of cash gain other than bloon pops. YMMV, but the 3|x village (Monkey Town) is debatable in this respect.
    • No Lives Lost can be a challenge on its own, but prohibiting spikes and pineapples ups the ante. Not selling towers goes further still by denies money and space refunds, meaning that careful placement and upgrading is required.
  • Any variant of NAPSFRILLS, including NAPS, NLL, and NAPS NLL, can be used not only for normal maps, but special missions, daily challenges, and random missions as well.
  • CHIMPS in BTD6 is short for No Continues, no Hearts Lost, no Income, no Monkey Knowledge, no Powers, and no Selling".
  • The Monkey Village upgrade Monkey Intelligence Bureau creates the acronym M.I.B. BTD6 Makes this more explicit with the upgrade icon being a monkey agent wearing a black suit— that is to say, a Monkey In Black.
• Fuuma Shuriken: Boomerang Throwers can be upgraded to use these in BTD3 onwards, though the game refers to as glaives. In BTD5 and onwards, they can also upgrade to homing fuuma shuriken, and then get two of them that permanently rotate around them, shredding anything that gets close.
  • The Ascended Shadow Ninja Paragon from BTD6 uses large shurikens that may or may not count for this trope.
• Fragile Speedster:
  • Pink and Yellow bloons. They are the only bloons in the entire series that are faster then the Ceramic Bloon, but they only have 5 and 4 layers respectively.
  • The DDT is definitely one of these with its rapid speed that's comparable to the pink Bloon (not to mention its lead and camo properties) but it's by far the second weakest MOAB-class bloon in terms of health, being taken down with only 924 hits. Of course, it is far more difficult to damage a DDT in the first place thanks to its wide range of immunities^note Those being immunities to sharp and explosive damage, as well as camo than to take it down once you can damage it.
• Friendly Fireproof: The monkeys are always immune to other monkeys' projectiles, no matter what.

G

• Game-Breaking Bug:
  • Attempting to move Pat Fusty via the Chinook ability while any submarines are underwater outright crashed Bloons TD 6 at one point.
  • A massive game-breaking bug was discovered in Version 25 of the game which was not patched until the next major update, which made it possible to use Challenge Editor codes to gain free Monkey Money and map badges. This bug was heavily cracked down by Ninja Kiwi, with all videos showing the bug being taken down and all codes created for the exploit deactivated.^note This was arguably justified as gaining free map badges and Monkey Money would harm the game's integrity and the wallets of the developers.
  • 31.0 Lych Boss Bloon Events were not fun to say the least, due to a bug where the Lych-Soul that spawns at every skull was being affected by freeplay ramping for Tier 3 and above (freeplay ramping buffs the HP and speed of MOAB-class bloons beyond round 81) when it normally should not have been. The result was a Lych Soul at Elite Tier 5 having 2.4x the HP and nearly 2x the speed it was normally supposed to have (and keep in mind the Lych Soul at Elite Tier 5 already has a massive 485,000 HP and moves slightly slower than a MOAB), resulting in a nearly unkillable Bloon that will take massive amounts of effort to kill even with multiple paragons AND a VTSG on the field.
  • In Version 31.2, it was discovered that by clicking the upgrade hotkey for a Paragon at the same frame as clicking another eligible Tier 5 capable of upgrading to a Paragon, you could create multiple paragons and thus be easily able to get to massive late-game rounds (with the YouTuber ISAB reaching round 1000 in a video uploaded here.)
  • Boss Bloon Event 55 was afflicted by this, where due to a bug caused by the reworking of Boss Event continues, caused the Round 120 retry option to appear free. Sounds good? Clicking it will practically ruin your account, as clicking the option to do so will instantly flag your account as cheating and lock you out from much of the game's online activities.^note The bug was the result of presumably sloppy coding where the implementation for the Round 20 restart option was added, the prices were copy and pasted, moving each checkpoint 20 rounds ahead. However, this did not apply to the Round 120 checkpoint, as there are no checkpoints after it, causing the checkpoint price to become zero, and due to the anticheat detecting a player using the retry for free, they will be flagged.
  • Possibly the most game-breaking bug in the game came in Version 38.3, which was the Quantum Entanglement bug. This bug with the Total Transformation (x5x alchemist) allowed you to link some transformable towers to whatever you want. If you link something to a dart monkey they become compatible with both Fan Club abilities, which allows you to greatly enhance the attack speed of the tower (Plasma Monkey Fan Club gives most projectiles the texture of the plasma balls, but this is only visual). You can also link almost anything to a bugged Wizard lord Phoenix and have the tower use its ability indefinitely, link to bosses and instantly kill them by selling the linked tower, and even link a True Sun God and enhance its sacrifices to the point where even maxed VTS Gs and degree 100 Paragons would look like a base tower in comparison by upgraded the linked tower.
• Game Mod: Several YouTubers have created and even distributed (now discontinued) mods for the Steam ports of BTD5. Here are some examples:
  • For BTD5 Steam, there's Revenge of the Bloons, which has changes such as faster juggernauts and glue being able to hit MOABs, However, the most notable change is that there are fewer rounds to complete on all difficulties, but the game is a LOT harder. In fact, it makes Impoppable Mastery nigh-, if not outright, impossible to complete NAPS, and still quite brutal with anything short of Double Cash!
  • Junior Monkey modded an SWF of BTD5 Flash to add Mastery Mode from the mobile and Steam releases, camo-removing Viral Frost, glue that affects MOABs, and ice wizards. The latter freezes normal bloons while popping them (like directional Snap Freeze) and can conjure Absolute Zero, only it can stall MOAB-class bloons as well!
  • He has since created a No Escape (Flash) mod, which makes the game like BTD5 Mobile/Steam's No Escape mission, in which the map has no exit, instead looping infinitely around itself. The upshot is that you lose 1 life per second if the bloons remain onscreen for too long. Specifically, this mod only contains tracks with loops in them (such as 3x Around and Countryside), and the game starts subtracting lives five seconds after the last bloon spawns, rather than 30 seconds into the round.
  • The Apopalypse Expansion mod, which gives Apopalypse rules (non-stop, no between-round cash) and pseudorandom bloon progression to the standard difficulty modes, with differing bloon progressions based on difficulty. The original Apopalypse mode is turned into the Harder Than Hard Impoppable difficulty like from BTD5 mobile/Steam, but even harder due to MOAB-class bloons having both double health and double speed! This will be really easy...
• Gameplay Automation: Later games have an option in the pause menu to let the rounds to advance automatically without having to confirm them each time.
• Game Plays Itself: In Apopalypse mode, the rounds advance automatically with no option to stop this in-game, even if there are bloons from the previous wave still on the map. Some versions allow you to save your game and come back between rounds, somewhat defeating a major part of Apopalypse.
• Golden Super Mode: The "Sun" path of the Super Monkey. Harnessing The Power of the Sun, it shoots golden eye beams and towers from this path are golden in color.
• The Goomba: Red Bloons. Slow and only takes 1 shot from anything to pop. It's the first type of Bloons you encounter in any game.
• Gotta Catch 'Em All: In 6, you can collect any possible upgrade combination as an insta-monkey. The game remembers which one you had before you played them, and if you manage to collect respectively all 64 or all but one upgrade for a tower, its border in the insta-monkey menu will respectively turn black or gold.
• Guide Dang It!: Has its own page.
• Guilt-Based Gaming:
  • In the Flash version of BTD5, the game displays this message when you try to quit a level: "If you quit, the bloons win!"
  • One of the messages shown between rounds in the second game tells the player they may not need to use every single type of tower to complete the game, but to think of all the programming and artwork that would be wasted if they didn't.

H

• Harder Than Hard:
  • Extreme Mode in BTD5 is a map difficulty reserved for what are usually considered the three hardest maps in the game: Main Street, Bloontonium Lab, and Tar Pits (unlocked at Rank 50, Rank 55, and Rank 60 respectively). The maps cost a fee of either 25 or 50 Monkey Money per play depending on the map you choose, and will reward you with insanely large amounts of XP and an achievement worth many Awesome Points. Playing these maps can be a big risk if you plan on investing lots of Monkey Money into upgrades, Specialty Buildings, and Special Agents.
  • Impoppable mode. Towers and their upgrades are very expensive (including their sell price being reduced), the bloons move even faster, MOAB-Class Bloons are absurdly strong, and you only get one life. Speaking of the latter, it's impossible to have more than one life. Also, there are 5 ZOMGs on Round 85 just to screw you over.
  • Mastery Mode, currently only in the fifth game. All bloons are one rank higher, but you don't get extra cash! Overlapping with Nintendo Hard, this is a mode of play rather than a standard difficulty. Translation: it can be played alongside Impoppable difficulty! Hope you're good at the game if you dare take it on, especially on the harder difficulties.
  • Bloons TD 6 has six Harder Than Hard modes, enough to form an actual Tech Tree with its Standard Hard mode.
    • Alternate Bloon Rounds, the first of the bottom branch of the tree. The game says it itself in one of the tooltips: "You know 'alternate' just means harder, right?" It spawns tougher types of bloons at earlier rounds than usual; for instance, vastly more camos appear early on, and Round 40 contains a fortified MOAB (which normally doesn't appear until 22 rounds later in Standard) which has doubled health and drops double-health ceramics upon death. Also, if you attempt to Freeplay, you will be slapped with a fortified BAD on Round 100 (which normally doesn't appear until one hundred rounds later in Standard).
    • Impoppable mode makes a return in Bloons TD 6 as the second mode on the bottom path. Not only are towers and upgrades even more expensive than on Standard Hard, you have only one life (the Mana Shield Monkey Knowledge formerly also gave 25 regenerating extra lives in Impoppable until it was nerfed to be disabled here). You also have to beat rounds 81-100 on top of rounds 6-80, with those last 20 rounds being blimp-infested rounds that introduce the DDT and the BAD.
    • The final mode on the bottom path is C.H.I.M.P.S. You can only play it in a track after you defeat Impoppable mode (which in turn requires you to clear Alternate Bloon Rounds and the standard hard mode), which alone should say its difficulty. Not only are you unable to use any continues, you can't lose any hearts, you can't earn extra income (so much for Banana farms), you can't use powers, your Monkey Knowledge is disabled, and you can't sell your towers. You also have to beat rounds 6-100, like in Impoppable mode, with these restrictions (but thankfully the upgrade prices are the same as Standard, not Impoppable). The game even labels this as "the true test of a BTD master". Good luck.
    • Magic Monkeys Only, the first mode on the top path, only allows you to use Druids, Ninjas, Wizards, Super Monkeys, Alchemists, and a Hero Unit to beat what would otherwise be Standard Hard Mode.
    • Double HP MOABs is the second mode on the top path, where all blimps have doubled health, and this stacks with the Fortified modifier that already gives double health in the first place.
    • Half Cash mode is the last mode on the top path, and it deserves its spot. All gaining of money, from Bloon popping to Banana Farms is halved. This includes cash gained from the Cash Drop power. This mode is far more difficult than someone who doesn't play tower defense games might think—it’s been jokingly called "Insta-Monkey" mode, as the mode is made a lot easier by using Insta-Monkeys. It used to be Half Starting Cash, and came between Magic Monkeys Only and Double HP MOABs; this upgraded version of the mode became so difficult that switched places with Double HP MOABs!
    • Boss Bloon events require you to go all the way to Round 120, and can take up to Round 139. They also replace the Rounds 40, 60, 80, 100, and 120 blimps with a special Boss Bloon with far more health than any bloon in the game, unique gimmicks, and activate a special ability every 25% HP lost.
    • Elite Boss events makes them even harder by multiplying their health more than tenfold and having their special abilities activate every 10% HP lost.
• Hazmat Suit:
  • The Glue Gunner starts wearing one once his glue starts splashing or gets corrosive.
  • Mortar Monkeys will get one when upgraded to Bloon Buster.
  • Dartling Gunners will also start wearing one once they get upgraded to lasers.
• Heavily Armored Mook: Fortified Bloons. This trait gives Ceramics and MOAB-class Bloons twice the health, and makes Lead bloons take four times as many hits to pop. Their appearance even changes to look as if they're wearing banded armor.
• Helicopter Blender: The Heli Pilot's Razor Rotors upgrade functions as this, chopping up layers of any bloon within the Heli's hitbox. This conflicts somewhat oddly with Pursuit targeting (the preceding upgrade), since most bloons won't get hit by the blades if the Heli is staying in front of them like how Pursuit targeting enforces.
• HP to One: A variation in BTD6. The Bloon Master Alchemist can throw potions that turn any bloon into a Red Bloon, including the ZOMG. It comes at the cost of not getting the cash from popping the bloons normally, though.
• Humongous Mecha:
  • The Technological Terror is pretty big compared to most other towers, and it's a robot. It also has green plasma that's stronger than the usual purple plasma. Its final upgrade in the sixth game is even stronger, able to destroy ZOMGs like they were nothing.
  • The final upgrade of the middle path of the Dartling Gunner eschews its Macross Missile Massacre for a mech suit with two BFG missile launchers.
• Hydra Problem: If a Regrowth Pink or stronger is not the original color regenerates, the new color will still contain as many bloons as it did before - for example, if a Regrowth Pink regenerates into a Regrowth Black and is then popped, two Regrowth Pinks will come out. This means that regrowth bloons must be damaged quickly, or they will swarm your defense and easily make you lose. The Monkey Apprentice is notorious for causing this with its lightning upgrade and both tornado upgrades. This feature can be Exploited to make round time indefinite for Supply Drop Sniper farming, or to grind money and Experience Points. Plenty of Advanced Challenges in BTD6 involve turning all Bloons into Regrowth and with a significantly higher Regrowth Rate (sometimes to the point they regenerate instantly), requiring the player to either remove the Regrowth trait or one-shot the Bloon altogether to win.

I

• I Am X, Son of Y: Quincy, the first hero from BTD6, periodically says that he's "Quincy, son of Quincy" if you tap on him.
• Infinity +1 Element: In BTD6, some upgrades change the tower's damage type into the "normal" damage type, which can pop all Bloon types. In some cases, this is granted implicitly without telling the players, like The Tack Zone, which used to be able to pop Lead despite its projectiles not looking any different from its previous upgrades (which are "sharp" types that can't pop Leads).
• In-Game Banking Services: The 2nd path upgrade for the Banana Farm is called the Monkey Bank. It gains in-game money over time and this money can be withdrawn at any point. If you build multiple Monkey Banks, you can withdraw all their money at once. They can be further upgraded into the IMF Loan and Monkeynomics, which have higher carrying capacity and allow you to loan out some money, although you have to pay it back. There's also a Monkey Knowledge upgrade that lets you deposit money into Monkey Banks and their upgrades, to get even more later.
• Instant Bandages: In BTD5, the ZOMG has a bandage appear over its skull design in its last stage of health.
• Intelligent Primate:
  • Dr. Monkey, a supporting character from Bloons Super Monkey 2 whom Ninja Kiwi sometimes mention in their blog posts that answer fan questions.
  • Benjamin, one of the heroes from Bloons TD 6*, is a hacker.
• Invisible Monsters: Camo Bloons aren't really invisible, but most towers will not be able to detect them unless there is a specialized tower nearby. However, several towers can be upgraded to have camo detection, while the Ninja Monkey, Spike Factory, and Dartling Gun (in BTD5) innately have this. In the fourth game where they were introduced, camos only existed as a single layer, and they could be hit by any tower, just not targeted by most; stray projectiles could still break camo layers, making them a lot less threatening so long as one can be hit to start a chain reaction.
• Irony: Lead Bloons can only be popped with explosions (not counting upgrades such as the Monkey Apprentice's Lightning Bolt or the Super Monkey's Plasma Vision). Lead Bloons contain Black Bloons, which are immune to explosions, nullifying the towers unless they are near a support tower that enables nearby towers in its radius to pop all bloons or have an upgrade which lets them pop black bloons, such as the Monkey Intelligence Bureau.

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