Invincible Minor Minion

""Warning: some enemies cannot be killed. Beware of these immortal creeps!""

- Super Mario Bros instruction manual

One of the lowest villains/monsters on the totem pole, yet either has Nigh Invulnerability, or a shield that protects part of its body, or all of it at certain times. Not a Boss Battle, the hero merely has to avoid them. They will still be standing when the Big Bad dies. People try to kill them for the challenge. Sometimes, the game will have a rare weapon or powerup that can take them out where the rest of the player's arsenal has failed.

Rarely is it explained why only the Mooks are Made of Indestructium while the higher-ranking villains remain killable. Also, it would make much more sense for them to be holding the key than the bosses.

Contrast Badass Bystander. Also sometimes overlaps with The Spiny. If he is killable, but very hard to, you have a Metal Slime. See Goddamned Bats for the typical opinion of these.

If for some reason you get into a fight with your own side's Redshirt Army, you may find to your horror that their being Friendly Fireproof makes them impossible to kill... but the same doesn't seem to apply to you.

The exact opposite of Fake Ultimate Mook. Often employed as City Guards if someone is needed to patrol the Broken Bridge.


 * The archetypical "piece" of a character is the Metool/Met helmet from Mega Man. Metools resemble a face wearing a construction helmet. While he could be beaten easily enough when he peeks out, with his helmet down he deflects all of Mega Man's attacks (except for latter Mega Man games starting in Mega Man X 8, where the characters have ways of getting through that defense and flip the Met over, exposing their vulnerable undersides.) Has led fans to wonder what the heck those helmets are made of, and why doesn't Dr. Wily just make a robot out of it?
 * In Mega Man 6, using the Power Armor mode of Rush armor lets you use a charged up punch to destroy a hiding Metool.
 * Gabyoalls/Spines are unaffected by all weapons save a couple. They're those low, disk things with two spikes that move faster when Mega Man's on the same platform. Also a spiny.
 * In MS Paint Masterpieces, a webcomic retelling of Mega Man, he did. It also goes on to say that the armor works by spreading the force of attacks and sending it around their body. Since Enker has multiple plates of armor, overloading him with energy while he has no way to get rid of it makes him explode.
 * Enker was actually a boss in the first Game Boy Mega Man game. Normally completely invulnerable to all weapons, one of his moves absorbs shots from Mega Man's standard Arm Cannon into his sword and unleashes a wave of energy as a counter, and only then do they damage him.
 * In 3 (DOS), there are turrets randomly placed around the levels, usually in platform-heavy sections. You can't destroy them, no matter how hard you try or with any of your special weapons. All you can do is stand in a safe place and memorize their patterns, and hope to dodge their insanely fast bullets/lasers. There is no "or".
 * In Mega Man 9, the Black Hole Bomb can destroy mets even when they are in the defensive posture.
 * The concept arises again in Mega Man Legends with the Servbots (some of them pictured above), mostly incompetent flunkies to the game's Goldfish Poop Gang. Completely invulnerable to all forms of damage. In the spinoff game The Misadventures of Tron Bonne you can exploit this by sending them into otherwise fatal dangers to retrieve treasure.
 * Bubbles from the The Legend of Zelda game were originally completely invincible. Later overhead games changed them into "Anti-Fairies" and often gave them an Achilles' Heel that often turned them into regular fairies. In Zelda 2 and 3-D versions they take regular damage.
 * Nothing can kill a wandering thief in the Lost Woods in A Link to The Past.
 * In many of the Zelda games, attacking the normally peaceful Cuccos will cause them to swarm and attack the player. Attacking one in The Legend of Zelda Twilight Princess earns you a brief lapse of not being a Cucco. They're indestructible, with rare exceptions
 * The giant black pig in Wind Waker is also immortal. The other two pigs are only half-immortal; you can't kill them, but they die anyway.
 * The original Super Mario Bros. It had the Fire Bars and Podoboos (fireballs), the latter being listed among the enemies in the manual (so not merely a trap). Super Mario Land and Super Mario Bros 3 had the trap-enemy Rotodisc, which could be killed in the latter game by using the Tanooki suit to turn into a statue and fall on it at the right moment.
 * Podoboos can be killed by the Starman. They even have a set amount of points they give by doing so. However, they only exist in maps where there are no Starmen, so the only way to do it is by hacking the code.
 * In The Lost Levels, there is one castle where you have the opportunity to kick a Koopa shell at one. You get points for the kill, but a new one spawns immediately in the same spot.
 * Boo Diddly as well, although they can be taken out with a Starman or with the Hammer Bros. Suit.
 * A number of fairly common enemies in SMB and SMB 3 may qualify depending on standards. In SMB 1 beetles are invulnerable to anything other than a kicked shell or being kicked themselves into a pit. In SMB 3 quite a few enemies are invulnerable to standard attacks and can only be killed with either a starman or hammers (or statue stomp), including thwomps, dry bones, and boo diddly. Jelectros and Munchers are truly invincible, but are immobile, making them as essentially living Spikes of Doom.
 * In Super Mario World, Boos and Big Boos can be killed by sliding down a hill at them.
 * While we're at it, Super Mario world also has Ball 'N Chains and Bullet Bill's third cousin, Torpedo Ted, the course in which they appear is practically a Painfully-Slow Projectile variant of Bullet Hell.
 * Super Mario Bros. 2 has "Phanto", who begins chasing you as soon as you pick up a key. However, he stops chasing you once you put the key down. He'll start chasing you again when you pick it up, so it's mostly a game of either out-running him or drop-and-pick cycles.
 * The GBA remake lets you kill off Phanto if you managed to snag a star.
 * In the original you can kill him by throwing the key at him. He'll come back, though.
 * The jumping and flying "Pluton" thieves in Kid Icarus.
 * As of Kid Icarus: Uprising, Plutons CAN be defeated, but they move so fast that it's rather hard to do so; plus they run away after a while, taking your stolen items with them. Instead, the newest Invincible Minor Minion is the Orne, which is not only invincible, but touching it is an instant death. Only the Three Sacred Treasures can kill them, and you use them only in one  chapter.
 * Gordos from the Kirby series are completly indestructible, even if you run into them with invincibility activated (which normally kills every other enemy in the game, including bosses). Gordos could be destroyed in Kirby's Dreamland, but the method for doing so was only available in the boss rush level and is unavailable in all future games, where the boss rush is separate from levels. Kirby's Dreamland 2 featured a boss that took on the properties of a gordo but had to sacrifice invincibility to actually attack.
 * Shotzos as well. However, unlike Gordos they follow more the rules of gravity, so you can send one down a bottomless pit if it's standing on a breakable block. But that is less common than how often you can have a Gordo fly offscreen.
 * Batamons in Kirby's Dream Land 3 are technically killable, but it's very hard to considering how little opportunities you have to do so. Mostly, they just happily march around behind solid walls.
 * "Dry Bones", a skeletal koopa appearing in multiple Mario games, simply collapses into a pile of bones rather than dying - he pops back up again not long after. Rather than avoiding the hero after that, you tend to have to avoid him instead. Like many "unkillable" Mario enemies, it can be killed via Starman invincibility, or in Super Mario World with a Cape swing.
 * In Mario 3, when they were first introduced, they could be killed either with a Starman or with the Hammer Suit.
 * The answer in the Paper Mario series? Kill It With Bombs!
 * Killable in Super Princess Peach using either the Rage Vibe or the Poundbrella ability.
 * In other words, they're immune to the Goomba Stomp and the fireball, which makes them considerably more annoying than many enemies, but they're far from indestructible.
 * Super Mario Land 2: 6 Golden Coins has invincible stars (not stars that turn you invincible, stars that are invincible and will kill you). Like Jelectros, they only appear in one stage, a frustrating auto-scroll. Unlike Jelectros, some can move. It also has Gordos, but they only shake a little when Mario comes near them and are not hostile.
 * Whether they hop or march, Tap Taps from Super Mario World 2: Yoshi's Island are virtually indestructible. The only way to get rid of them is to knock them into a bottomless pit or into lava or use a fire Watermelon or Ice Watermelon. Sure enough, when you face Tap Tap as a halfway boss, you have to knock it into the lava under the arena.
 * If there are several, you can knock one into the others to kill them.
 * Spitting or rolling a Pill Bug at them (like in 1-7) is one of the few ways to deal with them.
 * You'll face another one as a sub-boss in a scrolling level. Unlike the boss fight, there's no lava - only apparently bottomless pits. If you knock him in, he'll eventually jump out again.
 * Super Mario Kart had invincible Thowmps on Rainbow Road. Touching them made you spin out and lose coins. Even the Star item does nothing to them.
 * Mario Kart 64 had the same thing with Chain-Chomps. In fact, Chain-Chomps are this in every Mario Kart or any Super Mario Bros. game for that matter, with the exception of the RPGs. However, you can sometimes get rid of them by stomping the post they are chained to into the ground.
 * In Super Mario RPG, Chef Torte and his apprentice cannot be harmed - this is supposed to be a hint to the player that you need to attack Bundt - the actual Boss - and not them. Once you figure this out and do enough damage to Bundt, the two chefs flee.
 * Earthworm Jim had a couple, but the most remembered ones are probably the big brute cats in the Down the Tubes level. They can't be killed by anything except plasma, and there is typically a hanging ledge above the area they patrol. You usually have to hang onto said ledge and pull your body up to avoid detection from these guys.
 * Medi Evil 2 loves these, examples include the police officers, the vampire girls and the Mullocks.
 * An archetypal enemy in Castlevania is the "blood" or "red" monster, usually a skeleton. These enemies never die permanently - they simply collapse into a pile of bones, much like Dry Bones above, and get back up a few seconds later. Castlevania: Portrait of Ruin actually gave two ways for the player to kill Red enemies... one a special spell with a casting time so long that the only time you'll ever cast it is when it's required by the plot, and another a special weapon obtained by a late-game quest, when you probably will never see such an enemy again and wouldn't really care about the damage from any you do chance to encounter. Oh, and they give mediocre experience if you do take them out. You could also kill them with Spyha's ice spell in Castlevania III. Meanwhile, Castlevania: Curse of Darkness has an Innocent Devil that will randomly cast a spell that will destroy one undead monster onscreen, even the red skeletons.
 * Castlevania: Order of Ecclesia also has red skeletons, which can be killed, but only by using the dominus glyph union, which
 * The skeletons in Undying were the same way, they'd always get back up after being taken down with conventional weapons. The only way to lay them to rest was to cast Dispel on them while they were standing.
 * The blood skeletons in Terranigma function the same way. However, if you dish out enough damage, they stay collapsed and vanish offscreen.
 * The skeleton in level 3 of Prince of Persia. The only sure way to get rid of it was pushing it down a deep pit.
 * The skeletons in Prince of Persia 2: The Shadow And The Flame could be defeated, but, like Dry Bones, they would get up a few seconds later. These skeletons also appeared in the Super Nintendo port of the original Prince of Persia, in which the level 3 skeleton is finally destroyed by a crushing trap.
 * The last skeleton in the final cave level was, like the skeleton in the first game, completely invincible (it didn't even have a life bar). The only way to get rid of it was having the bridge on which it stood collapse.
 * Level of the same game has an invincible floating Flaming Sword that attacks you at one point.
 * The bull from Banjo-Kazooie.
 * Snacker, the shark in Treasure Trove Cove and Rusty Bucket Bay, who appears out of nowhere if you enter certain areas with water. He can be defeated with certain weapons, but he'll reappear in about a minute, and can swim much faster than Banjo can. It's usually best to avoid the areas where he appears.
 * The living pipes in Rusty Bucket Bay not only can't be killed, but they can hurt you when you're using Wonderwing, which is supposed to make you invincible (though that part could just be game designer oversight.)
 * Some of the enemies in Banjo-Tooie are impossible or all but impossible to kill. Being able to kill them wouldn't help much, given the speed with which enemies respawn in Banjo-Tooie.
 * The Rippers of Metroid can be frozen, but not destroyed. (Except with the Screw Attack or Shinespark.)
 * Or super missiles, at least in Super Metroid and Zero Mission.
 * The shadow at the fireplace and the dancers in Alone in the Dark became this if you ever touched them.
 * Since the first game was basically H.P. Lovecraft brought to the computer screen, MOST enemies were either undefeatable menaces you had to avoid, or require so much ammo that you're generally supposed to trap or avoid them instead of defeating them.
 * An effect somewhat undermined by the substantial stunning effect of player melee attacks, which allowed a player with good timing to brutalize said abominations through fisticuffs repeated bitch slaps.
 * Tyrian would make some of its later boss battles tougher by introducing a small but invincible enemy with good firepower but extremely poor targeting ability. Sounds pretty par for the course, but it ran around the bottom of the screen and shot upward, forcing you to evade fire from at least two directions.
 * World of Warcraft:
 * The Cleaner, a black demon who suddenly spawns (Sometimes in groups!) if someone besides the one undertaking one of two particular quests is interfering with the goals and mobs involved. This has lead to some very creative griefing. He was removed in a patch in 2010.
 * Wintergrasp was also home to a invisible enemy that would sometimes for no apparent reason attack players. While it dealt little damage, it would also cause the target to be stuck in combat while in the zone. It was actually possible to go back to Dalaran and get killed by the guards for being in combat... in a sanctuary zone! This was most likely a bug and removed soon after the introduction of Wintergrasp.
 * Another bug-induced case of this trope has to do with how mobs react to damage. If they cannot reach the attacker, they'll start evading every attack. This, combined with mobs occasionally becoming stuck, can cause random enemies to be invincible to all damage until the next server reset (although they can't attack anyone, either).
 * There's also a version where they become able to attack from a distance but are always too far away for the player to attack.
 * In Blasted Lands, there are mobs specific to quests in the area. If you aren't on that quest and you try to kill them, they'll keep taking damage after their health runs out, but they won't actually die, just stand there on fire until you leave.
 * Silent Hill 4: The Room has Victims, the lingering ghosts of people killed by "The Man in the Coat". They cannot be destroyed completely, and attacking them only stuns them for a few minutes at best before they get right back up and start chasing you again. Just being near them causes damage to Henry (he'll put a hand to his head and the screen will flash whenever he gets too close). While Saint Medallions and Holy Candles will temporarily ward them off, Saint Medallions eventually break and become unusable, and you'll need all the Holy Candles you can lay your hands on once The best line of defense provided to you are the Swords of Obedience—there are only five in the entire game, and you're required to use one against a specific Victim in order to progress.
 * The Rawshocks from Shattered Memories are a subversion in that they're literally the only enemies in the game.
 * Half Life 2 and the Episodes have several cases.
 * Half Life 2 has a scene where you're near a lighthouse and the Combine is shuttling soldiers in on dropships. The only weapon in the game that can destroy the dropships themselves is a boat-mounted machine gun, which you had to abandon several hours ago. Even though the dropships are fitted with anti-personnel weapons, they return to base after unloading their troops, only to be replaced by not-invincible-at-all gunships.
 * The sentry turrets in the game can only be defeated by knocking them over either by throwing a grenade or shooting them from the side with enough force. You can't actually kill them. They will resume their function when placed upright.
 * You can also defeat them with either fire mode of the gravity gun.
 * Schroedinger from Hellsing has the dubiously enviable ability to teleport into enemy headquarters, be thoroughly dispatched via BFG, and reappear next to the Major to report. He later seems to have redirected his abilities towards
 * In Tales of Phantasia, there is one enemy in the Moria Gallery area, known as 'Urchin', that takes the form of a tiny green worm. However, the green worm is both practically indestructible and very dangerous—it's able to deliver 9999 damage to any character it touches, killing them instantly.
 * Except Arche, who flies. Sucks to be the party that decided not to include her.
 * And even then, you would have to have packed a specific item, and be fast, to beat it;
 * In Super Smash Bros. Brawl's adventure mode, there are is a kind of enemy called Jyk that moves in a certain pattern, damages you when you touch it, and cannot be hurt. They still count as enemies, though.
 * In Cave Story, Basil races back and forth across the bottom of the Egg Corridor and can kill you in one hit. You can't kill Basil.
 * There's also
 * In the first Halo, Cortana will summon invincible marines, and seal the doors, if you kill Captain Keyes in the first mission. You can unload every round in your gun on them, and they'll still be fighting you. Strangely they still bleed, so you can have situations where the marine you're fighting has a gallon of blood at his feet, but strong as ever.
 * Iji has "Blits", feral chunks of Nanomachines that eat other nanomachines. Only one weapon in the entire game can kill them, although one log comments that it is possible to launch them into outer space and they'll eventually starve into... "whatever it is, it's not recyclable."
 * The Bubble Bobble video games have (up to two) Baron von Blubba/Skel-Monsta, an invincible whale skull which chases the protagonists when they cannot defeat all of the enemies in a level. He has been promoted to Sequential True Final Boss status in two games.
 * Impossamole: Many of the Goddamned Bats and Demonic Spiders, including the sword guys in Orient, the swarms of ghost pirates in the Bermuda Triangle, and any underwater enemy. The Amiga/C64 version has both killable and invincible variants of many mooks, such as bats and skeletons, and they're hard to tell apart.
 * On the higher difficulties in the 3D Ys games, in addition to the color-coded enemies, there are black enemies that are completely invincible.
 * In the first Commander Keen trilogy almost all robotic enemies were impervious to damage, even the ones that could only push you around. In the second, most unkillable enemies were the tough rather than minor ones, but the sneaky rocks might count for only being vulenrable when they were already jumping at you.
 * The sneaky rocks were also vulnerable while they were walking around. To kill one, all you had to do was stand far away, shoot at him and immediately turn your back on him. He'll open his eyes just in time to see that neural stunner shot approaching before it hits him square in the face.
 * Terra Cresta, in its later areas, has goddamned spiked balls that (temporarily) sorround you, slow you down, and prevent you from firing.
 * The time-traveling FPS Darkest of Days has Opposition Agents, enemy time travelers equipped with futuristic weapons and armor, not to mention energy shields that are completely impervious to the period Civil War and WWI era weapons you're equipped with. Whenever they show up, your only option is to run like hell. Killing "blue aura" characters also causes them to teleport in to kill you, as a sort of Video Game Cruelty Punishment.
 * Later in the story,  They're difficult to fight with period weapons, but doing so can be very helpful.
 * In Donkey Kong Country 2, red Zingers can only be killed with barrels full of explosives or with the assistance of a "!" invincibility barrel. They can even survive being jumped on by a rhino. Looks rather silly when the boss version of the Zinger is can be defeated.
 * The original game has Stop and Go Station, a level designed entirely around invincible enemies. Rock-Crocs (Kremelings made of stone, with Glowing Eyes of Doom Red Eyes, Take Warning) infest the mineshaft, pacing back and forth for all eternity. Get in their way, and you're toast. The only way to deal with them is to touch the floating barrels to get them to change from a green "GO" to a red "STOP", which causes the Rock-Crocs to fall asleep. This only lasts for a few seconds, so you must race from barrel to barrel to avoid getting hit. It's not really that difficult, but is infamous for being one of the scariest parts of the whole series.
 * In the Japanese version, these enemies can be defeated with Donkey Kong's handslap.
 * Similarly so were the skeletal kremling phantoms you find in the mine shaft levels of the haunted woods area. These guys are nigh invulnerable to any attack or thrown object you have (not that you could throw anything since you meet them in the middle of mine cart tracks) and will kill you if they touch you, which is easy since they chase you for portions of the time you're in the cart. The only way you can avoid being killed by them is by beating the time you get from the beginning of the phantom's chase portion (marked by a door you enter) and make it to that portion's "exit" (another door) before time runs out. If not, that phantom will automatically kill one of your kongs.
 * The blood-red piranha, man. Most underwater enemies are unkillable unless you ride/are a certain animal buddy, but the blood-red piranha is both VERY fast and out for your blood. Gallons of Nightmare Fuel were had.
 * In The Godfather: The Game, you may occasionally encounter mooks who you can't touch at all even though their stated rank is below what you may be routinely slaughtering by then. Fortunately they almost never show up in real combat situations.
 * Thunder Force IV had these in the lava cavern stage. Part of a larger mook, these things would break off once destroyed, and then orbit around the player character, blocking your shots. The only way to defeat it was to lure it into the walls, doing collision damage to them and eventually killing them.
 * In the "Siren" series of games, every enemy in the game (the "Shibito") are undead and cannot be killed by conventional means; at best you might pin one down by staking them to the ground under the right circumstances, bury them alive, or something similar; only a couple of characters ever gain access to anything paranormal that lets them destroy them for good. Every other time, you can only stun them. Shoot them as often as you like or smack them with a melee weapon, and they only temporarily go catatonic until they inevitably heal themselves minutes later.
 * Wubbas in DROD: Journey to Rooted Hold.
 * Forsaken plays with this trope in the Space Station level. On your way out, there's a little mouse droid roaming one of the rooms. Mo matter how much you shoot it or what you shoot it with, it will not die. The game will display a message asking you if this little critter is really that annoying that you feel the need to kill it.
 * Left 4 Dead had a glitch that would occasionally cause a random Common to become invincible. As if that wasn't bad enough, the AI teammates didn't even notice that Common anymore, and it could kill them. The only was to escape would be to shove the invincible zombie into a closet, and then run. Luckily, this glitch has been patched.
 * Eversion's rock monsters are completely immune to any attack at all, and only pause for a second when you hop on them.
 * In Berzerk, if you hang around on a level too long, Evil Otto (an invincible smiley face) shows up and homes in on you, forcing you to move on or die.
 * Evil Otto becomes killable in the sequel Frenzy with three hits, but when you do, another even faster one immediately appears, and should you attempt this in the room featuring the Giant Mook version of Otto, you'll be immediately swarmed and killed by several lightning-fast Ottos.
 * Smash TV has faceless drones that behave basically the same way.
 * In Pathways into Darkness, Banshees are impervious to physical attacks, while the Green Oozes and "Giant Purple Hellbeasts" encountered on "Earthquake Zone" are completely invincible. The Oozes avoid you if you consume a poison potion.
 * From Purple, there is a family of rolling barrels, trashcan mooks and spikeballs in the sewers. Of them three, only barrels can be destroyed using the moon item.
 * Dead Rising 2 features looters that are only marginally tougher than zombies - except if they're behind the counter of their stores (which somehow makes them invincible.)
 * Bug!! Only one that's actually an enemy as the other "invincible" enemies are traps of sorts. The spiny lizards of Reptilia could not be killed via any means. Not even the Zap Cap, or Stunt Bug would even touch them. Your only option was to avoid them like the plague.
 * In Dead Space, when the Hunter gets unleashed on you, you blow off its arms and legs like any other necromorph mook and turn to leave. Then you see it regrowing its limbs. Oh Crap.
 * In the sequel, you meet another variant of the Hunter, a little leaner and faster, and with three glowing red eyes glaring at you from its not-quite-a-face. Your usual strategy is to hack off the legs, time-freeze it, then book it out the nearest door and hope you get your breath back before it gets scripted to jump on your head again. Fortunately, it's NOT scripted to jump on you if you get it stuck behind the airlock leading to the last fight.
 * Digimon World 3 has the Knightmon guarding Amaterasu City. To engage one in battle is effectively suicide, as you cannot win. Period. They are not even beatable via hacking.
 * The Tower of Druaga has the Will O'Wisps, which appear if you take too long on any floor and are present from the start on some floors. Incidentally, three items counter the Will-o-the-Wisps in question, but if you miss even one of them, you won't make it past floor 59. Oh, and the second of these three items negates the effect of the first and is required for the third, which combines the effects of the first two.
 * Bacura, the floating mirror panels from Xevious. It is also invincible in Tales of Symphonia except for its rare Metal Slime appearance outside the mines.
 * The Skeletons in the Catacombs in Dark Souls can be killed, but they'll keep resurrecting until the nearby necromancer is slain. They can also be permanently destroyed if they are slain with a Divine weapon.
 * The Knaaren in Rayman 3 are invincible, but their champion Reflux can be defeated in the most epic bossfight ever. And then again later after he becomes even more powerful.
 * Battletoads for NES had the rubber ducky of doom, who could not be killed - just flipped over when defeated, comintg to its sences few seconds after. Oh, and you could attack it only from behind, otherwise it unleashed a vicious lightning-fast pecking assault which could send your toad crashing through the wall.
 * And then there's Scuzz, who you race in Rat Race, and who can only be killed with a very-hard-to-pull-off glitch.
 * Snailiad has the Jellyfish and the spikeballs, though this is subverted when you get the Devastator.
 * Some of the panels in Parodius have so many hit points, it's impossible to kill them before they leave the screen. Gokujyou Parodius takes this up to 65536 by giving us the 16-Bit Block.
 * Munchers, Spikitus and Boss Bass in the Something series. These mooks get levels dedicated to them.
 * Boss Bass appears as the main enemy in "Dat Bass!" He's more difficult to handle because he's now immune to fire.
 * Most of the obstacles in Hungry Vegetation are Munchers. To make things worse, some of them fall out of the sky and cover up various areas.
 * Spikitus are the main adversaries of Spikitu's Castles 1+2. They're immune to fire and they can't be stomped.
 * Thief II : The Metal Age has Mechanical Cherub. It's a small golden robot in the image of a boy. Which does not talk, but makes noises. It cannot attack, cannot be damaged by any known means (but can be flash-bombed or simply locked up in a room), but follows Garrett around and may run for help if detects a guard. Oh, and it first appears literally out of thin air after.
 * Hulks in Robotron: 2084; unfortunately, they are the only enemy that can kill the Humanoids you are supposed to protect. Worse, there are stages where enemies are mostly Hulks.