Mazinger Z provides examples of the following tropes:
Macross Missile Massacre: Ashura and Brocken's ships and many kikaiju tried that tactic against Mazinger Z. Results varied.
And in the short story New MazingerMazinger-Z itself used that tactic against an army of monsters.
Made of Explodium: Many Mechanical Beasts exploded easily -and spectacularly- when defeated even if there was no reason for it (other than animating spectacular explosions, of course). Aeros B3 reinforced this trope: it was loaded with explosives since its purpose was diving into Mount Fuji and exploding inside to awaken the volcano and bury the Institute under a tidal wave of lava. A subversion was Balanger M1, that were clusters of underwater, guided mines that did NOT explode but stuck to their target and shocked it with electricity. Several Warrior Monsters and Saucer Beasts from Great Mazinger and UFO Robo Grendizer also followed this trope.
Made of Indestructium: An early Anime example. Mazinger Z is made with Alloy Z, an alloy made of Japanium, a rare metal that can only be found in Japan. Dr. Kabuto discovered the metal and built Mazinger Z with it, thinking Mazinger would become indestructible. Throughout the series, the mecha got hit by giant monsters, missiles, bombs, got burned and electrocuted, got dumped in lava and doused in acid... and even though it got damaged every so often, the Alloy Z endured all of that until the last chapter, and kept Kouji alive. Several times Dr. Hell and his Co-Dragons would try and get their hands on a sample of Alloy Z to build his Robeasts with it because Mazinger's armor was too tough to break, shatter or dissolve easily otherwise. The concept of chogokin ("Super Alloy") became so pervasive and widespread all Super Robots followed Mazinger were made of chogokin, and it baptised one whole toy line.
Mad Scientist: Big Bad Dr. Hell. Dr. Heinrich, who collaborated with Dr. Hell and built a Humongous Mecha to defeat Mazinger and prove he was better than Kabuto. And, in some versions, Dr. Juzo Kabuto as well.
There's another case in Lorelei, Shiro's first love, whose father was a very aloof foreign scientist who's also Covered with Scars. And then we learn that not only she's a Robot Girl, but when her father is killed and begs her to have revenge. It ends up in tears.
Mad Scientist Laboratory: Dr. Hell's lab, installed in his base. It was barely seen in the series, though. Dr. Kabuto's lab in the original manga also counts.
Make My Monster Grow: In episode 12, Baron Ashura used a size-changing ray to turn a tiny robot into a giant Robeast -Bicong O9-. That ray had been invented by Dr. Hell, who previously tested it with Ashura himself/herself, briefly transforming it into a giant. Throughout the series, Big Bad Dr. Hell used more Mechanical Beasts that could increase their size.
Male Gaze: Often the camera lingered on Sayaka's behind, especially when she wore skirts. It also lingered on women when they were wearing a towel after a shower or changing clothes. Of course, it also happened in the sequels. Given that Mazinger's creator introduced Fanservice in the anime, it was to be expected. But to be fair, there also were plenty instances of Female Gaze in the series, specially in regards to Tetsuya and Kouji getting several Shirtless Scenes.
The Man Behind the Man: In the original manga, Baron Ashura shows up before Dr. Hell, leading several Mechanical Beasts and the Iron Masks troops and calling it "Ashura's army". In that chapter he seemed like the Big Bad, but one chapter after Dr. Hell is introduced and we learnt Hell was behind the whole operation and he is the real Big Bad.
In the anime, Archduke Gorgon was apparently a Dr. Hell's ally. In the last chapters we learnt he was a Dragon with an Agenda was working for a Greater Scope Villain, Great General of Darkness/Ankoku Daishogun.
Meaningful Name: Professor Kabuto describes the titular mecha as being powerful enough to make its pilot a devil - "Ma" in Japanese - or a god - "Zin". This is also the first line in Mazinkaiser's first theme song.
Also, "Kabuto" means "helmet" in Japanese, alluding to the way Koji activates Mazinger by landing his Jet Pilder on it's head like, you guessed it, a helmet.
Mecha-Mooks: Most of the Mooks were Cyborgs, but several of them were Ridiculously Human Robots such as the Gamia sisters, Erika, Lorelei or the Robot posed like Kouji.Just a Machine was subverted: When Kouji killed the Gamias, they were so human-looking he felt sickened and disturbed. And he felt sad when some of them died. Also, they were or were not Made of Explodium depending on the robot. Erika did not explode; Kouji robot did, though.
Mecha Expansion Pack: Probably the originator of this trope: its Jet Scrander is basically a giant robot-sized jetpack, and it was created when Dr. Hell started creating more and more flying Beasts to attack a Mazinger which was helpless against aerial attacks. Go Nagai stated he always intended for Mazinger to fly, but first he needed to establish that the mecha was heavy, so he whitheld the Jet Scrander until it was clear that Mazinger was not light.
Men Use Violence, Women Use Communication: In the Mazinger trilogy male characters tend to resort quickly to violence to solve a conflict whereas female characters tend to look for alternate, peaceful means to solve it or regret when a peaceful outcome seems out of reach:
In Mazinger Z episode 3 Sayaka tested Aphrodite-A's new weapons and stated that she wished that Aphrodite was only used for peaceful purposes. In the prior episode Koji swore that he would use his Super Robot to fight Dr.Hell.
King Vega was convinced that invading and conquering other planets was the only way to find a new home to his subjects after their homeworld's demise. Duke was convinced that the only way to stop them from invading Earth was fighting them. Rubina -daughter of the former and ex-fiancee of the latter- thought that mutual annihilation was the only possible result of that war. So that she did find an alternative option and tried to talk both into a ceasefire. It did not work.
In a manga story, Duke has to fight brainwashed Kouji and Tetsuya. Meanwhile, Hikaru laments that there is no way that peace can result from that battle, not matter who wins.
Mentor Occupational Hazard: Dr. Kabuto dies in the FIRST episode after handing Mazinger Z over to his elder grandson. Justified as he was gravely injured before said handing.
Mid-Season Upgrade: Several of them. Mazinger Z was routinely upgraded to allow it fight on different enviroments successfully or to endow it with new weapons to fight increasingly powerful enemies. The most promintent of those upgrades was the Jet Scrander.
Might Makes Right: In a story arc of the Gosaku Ota manga alternate continuity where Baron Ashura managed to kidnap Kouji he revealed this is how he thinks that the world works. The strong defeats, dominates and exploits the weak. The weak dies, the strong survives, and that is how it is. Therefore, "good" and "evil" are empty words. This is how he excused/justified his crimes.
Mind-Control Eyes: In the Mazinsaga, brainwashing, mind-control and hypnotism happened constantly. Usually the way to show the color of the sclera changed or the eyes became completely blank. An example was when Boss was hypnotized by Mechanical Beast Gumbina-M5: his sclera became greenish-yellow instead of white, and his pupils dilated.
Mind Probe: In the UFO Robo Grendizer vs Great Mazinger feature film, Kouji was kidnapped by Barendos, who used a mind-probing machine to extract information about Grendizer and the other Earth's giant war mechas -Great Mazinger and Mazinger Z- from him.
Missing Mom: Kouji and Shiro's mother died in a laboratory experiment went wrong. Likewise, Sayaka's mother is nowhere to be found and she and her father live alone, so it is implied her mother died or left.
In episode 90, Dr. Hell fabricated a cyborg looked right like her and sent it to the Institute in order to wreak havoc while he made preparations for the final battle. Naturally, that stratagem caused much grief, especially to Shiro.
And in Shin Mazinger Kouji and Shiro's mother shows up and gets named -Tsubasa Nishikori. And it is revealed Kouji has inherited his Badass traits from HER.
Mistreatment-Induced Betrayal: Baron Ashura was mostly loyal to Dr. Hell, who felt that he was aboveexecuting his subordinates but not of punishing their failures with strikes, insults or torture. Due to this, Asura sometimes got fed up with being mistreated and mocked and he/she disobeyed orders or acted on his/her own (the final time was when he/she stole the fortress Ghoul to make a kamikaze attack on the Institute in order to show all, Dr. Hell and his/her enemies, who he/she was. In the Gosaku Ota alternate manga, he/she went a step beyond that and he/she decided to betray Dr. Hell and Take Over the World on his/her own because he/she was "sick of that crazy old man and that headless idiot (Count Brocken) always mocking him" and he/she intended to give them a lesson.
Mobile-Suit Human: A variant occurs in New Mazinger: the titular Super Robot is blasted into a sword-and-sorcery world where he rescues a topless princess (this IS Go Nagai, after all) from invading lizard-men. When the princess attempts to offer herself to the mysterious knight to persuade him to aid her people, he reveals that he is a machine piloted by a human "just the right damn size for a pet!"
The Mole: Dr. Hell had moles installed in several countries, usually infiltrated in centers of scientific research but also in army bases. The most infamous were Rico, an android Dr. Smith -a New Yorker scientist- had hired like his assistant and later infiltrated in the Photon Atomic Power Research Institute to sabotaging the JetScrander, Erika, a female android was supposed to infiltrate into the Institute but got amnesiac and befriended Kouji, and several androids impersonated several characters in order to wreak havoc (such like Professor Yumi, Dr. Smith or Kouji and Shiro's mother).
The Mykene Empire also had a mole infiltrated among Dr. Hell's henchmen, Archduke Gorgon, and Marquiss Janus tried to infiltrate into the Fortress of Science once by pretending to be an average human girl.
And in Shin Mazinger Zero Dr. Hell created a mole believing she would work for him but in reality she was a Reverse Mole was always on the heroes' side and was only biding her time before defecting the first chance she got: Minerva-X.
Monogender Monsters: Nearly all Robeasts in the trilogy were male. Even Rhine X1 (Donau Alpha 1 in the original manga), a Mechanical Monster controled by a girl, was male. Maybe the only exception is Marquisse Janus, one of the Co-Dragons of Great Mazinger: her Humongous Mecha was clearly female-shaped.
Monster of the Aesop: In episode 41 Kouji is undergoing a hard pilot training to be able to fly Mazinger-Z at high altitude. However he resents many aspects of the training, like being on a diet, and he even got in a fight with Sayaka because she wanted him to eat the diet food she had made and he refused. Of course, in that episode Dr. Hell designed a Mechanical Beast -Karma K5- capable to fly higher and faster than Mazinger-Z, and The Dragon Count Brocken crafted a strategy to exploit that advantage. Kouji got hurt and even fainted due to physical strain and exhertion, and later he apologized to Sayaka, admiting he should have listened to her and eaten the meal she had fixed.
Monster of the Week: Subverted. Several times Dr. Hell sent several monsters instead of one to attack Mazinger-Z simultaneously. And in the original manga, Kouji fought several monsters at once more often than not.
In the Mazinger Z vs Great General of Darkness feature film, the Mykene army struck Paris, London, New York, Moscow and Tokyo. During their attacks, the Eiffel Tower, the Big Ben, the Empire State Building and the Tokyo Tower got wrecked.
In the Mazinkaiser movie, the first shot features Paris and the Eiffel Tower burning. The next scenes depict the main characters trying to fight the Mykene War Beasts in different locations. During the battles, the Statue of Liberty crumbled down, a pyramid got its top sliced off, and a chunk of the Great Wall blew up. Later on, Kouji and Great General of Darkness wrecked the Mount Fuji when they fought.
In the first appearance of Great General of Darkness in Shin Mazinger Zero, he split the Mount Fuji in two halves with a single stroke.
Mooks: Baron Ashura's Iron Masks and Count Brocken's Iron Crosses.
Mook Chivalry: In the anime adaptation, the Iron Masks were pretty pathetic. They always attacked Kouji Kabuto -or his friends- in the same way- noisily charging from the front-, never tried to overwhelm him with sheer numbers and stood quiet when he was making a pretty obvious attack. They wore weapons -swords and rifles- and helmets and Kouji fighting bare-hand still kicked their butts. Subverted in the manga, though, since sometimes they could be competent. In one of the first chapters Kouji nearly got murdered by only three of them that sneaked into his home overnight (and while two of them engaged Kouji, the third remained hidden to launch a surprise attack when The Hero was distracted). Kouji actually got to be rescued by a secondary character that pulled a Big Damn Heroes moment.
Motion Capture Mecha: Showed a primitive form of this. Although Kouji used a pair of joysticks and an array of buttons, levers and pedals to move Mazinger-Z, often Mazinger mirrored his motions inside the cockpit and vice versa (one example happened in an episode where a Mechanical Beast burrowed into the ground to try to escape. Mazinger-Z grabbed the Holzon V3's legs and leaned his body and head backwards as it struggled to pull the Mechanical Beast out of the ground. Inside the cockpit, Kouji was in the exact same position, doing the exact same thing).
Mundane Made Awesome: Although Kouji mostly saves his hotbloodness to when he is fighting or riding his Humongous Mecha, he simply can not make some activities in a mundane way. He does not go downstairs like a normal person, he slides down the railing. His idea of bike-riding contests includes hopping off the bike and making a somersault before landing back on his seat, or leaping across a cliff and using his rival's bike to gain momentum. And when he is going to docking in his Super Robot, he ALWAYS has to shout "Mazin go!" out of the top of his lungs in spite of it being unnecessary. And because he is the Trope Codifier for The Hero in Humongous Mecha anime, that kind of attitude bled into other Mecha Show protagonists.
And then you get Boss inventing Brockenball. It is like soccer, except the ball is Count Brocken's head and everyone wins... except Brocken who is the ball.
In one scene (based on the original manga) of a ''Mazinkaiser episode, Sayaka's bra gets cut, and everything -her bra falling, her breasts weirdly bouncing, everybody reacting to the fact- goes bullet time.
My Friends... and Zoidberg: Hilariously inverted every time the villains told a sentence along the lines of "Go ahead! Finish Mazinger-Z... and the other two robots!". The other two robots being Aphrodite-A (or Diana-A) and Boss Borot.
My Hero Zero: Awfully subverted in the Shin Mazinger Zero spin-off. Mazinger Zero is what Mazinger-Z may potentially become: an Eldritch Abomination. It happened in the spin-off, after Kouji crossed the Despair Event Horizon. He got in Mazinger-Z and fought like a relentless, raging berserker, fueling Mazinger's consciousness with a stream of negative emotions -rage, grief, despair, bitterness, pain-, until Mazinger-Z awoke, and turned into a demon. The results were... not pretty.
Naked People Are Funny: In one manga episode, several characters (Boss being one of them) strip themselves for absolutely no reason. Since Go Nagai introduced and made (in)famous the trope in manga, that gag was entirely expectable.
Near Villain Victory: Often Dr. Hell and his followers were on the brink of winning, and only through of extreme competence and sacrifice of Kouji and his allies or of utter incompetence of Hell's minions, the situation was saved. It happened several times when they very nearly took the Institute over (the most prominent of them happened in episode 57) or invaded it successfully (episode 87), or managed to steal a sample of Alloy Z... However the most notorious of them happened in the last episode when Archduke Gorgon's Robeasts destroyed Mazinger-Z and demolished the Institute. Tetsuya's Big Damn Heroes moment saved Kouji's life, but the villains finally were victorious against Mazinger. That story was greatly expanded in the Mazinger vs Great General of Darkness movie.
Nerves of Steel: The Professor Gennosuke Yumi. Eighteen-meters-tall killer robots are advancing towards his Institute? Mount Fuji is about of erupting and burying them under burning lava? Squads of armed soldiers are besieging them under the threat of set off an earthquake under their feet if they do not surrender? A spy is aiming one gun towards him? He has been captured and is being used like hostage? It happens all the time! Basically Yumi is a scientist, hence he refuses panicking and instead of it he uses his analitycal mind to study the trouble and find a solution quickly. He is so good keeping his cool he can come across like cold and aloof sometimes. Usually he only expresses emotion when one of the kids -Kouji, his daughter Sayaka or their friends- are in serious and inmediate danger.
Usually you would not associate Kouji Kabuto with this trope since he is a Hot-Blooded character, but he is surprisingly good keeping his coolness when he needs thinking quick to save himself or someone else.
Never Found the Body: Kouji, Sayaka and the remainder characters never found Dr. Hell's body and assumed he was dead. Granted, it would be hard to search and find his body given that in the original manga his Super Villain Lair / Humongous Mecha got blown up in middle of the ocean; in the anime series, the Cool Airship where he was fleeing got blown to bits and the remains sank in the ocean; and in another manga version, he was inside of his Super Villain Lair as it drifted spacewards, bleeding to death due to a stab wound. Still, he returned at the last season of Great Mazinger like The second Dragon-in-Chief of the Big Bad.
In episode 31, the bus where three workers of the Institute commuted crashed. The police believed they died, but Prof. Yumi refused to believe that because their bodies were not found. He was Genre Savvy.
Never Trust a Trailer: The show used extreme hyperbole in its next-episode previews, and was not above outright lying to the audience to hype up an episode. The most famous example is an episode called "Koji Kabuto Dies in Lava!"
This one is so infamous it was endlessly mocked and parodied, culminating in one of the Mazinkaizer stage in Super Robot Wars J being called "Kouji Kabuto Dies in Lava!?"
New Transfer Student: Kouji transferred to Sayaka's high school after his first battle in order to live closer to the Institute.
Nigh-Invulnerability: Mazinger-Z was not SO indestructible as Mazinkaiser. Still, he was sturdy enough to withstand a nuclear blast at point-blank range. However, it ultimately subverted the trope: Dr. Hell crafted increasingly more powerful Mechanical Beasts were capable to seriously harm Mazinger, and finally the Mykene War Beasts destroyed Mazinger-Z.
Ninja: Blazas S1 and S2, two way-smaller-than-usual Robeasts Dr. Hell built for a sabotaging mission in episode 46. He especifically stated that they were ninjas. Although not very stealthy (three-meter-tall, blue-and-yellow Mechanical Beasts tend to stand out ◊), they played the part, leaping around over walls and from branch to branch, throwing shuriken and infiltrating into the enemy base.
Nintendo Hard: The SNES game. One single life. Very sparse recovery items. No 1-Ups. No continues. No password system. No save system. If you die, you have to start again from the beginning. Have fun.
No Delays for the Wicked: Dr. Hell only has to worry about his subordinates doing how they are told and not betraying him. He has not to worry about them delaying or running in some kind of trouble or unexpected event that ruins the operation, or mishandling, losing or breaking down the technology and equipment that he hands over to them. They will always arrive at the appointed place at due time, and no operation will fail due to lack of coordination between several squads (although once, in an alternate manga version, an operation failed because one of his Co-Dragons took too long to be ready and the another lost his patience and attacked before time). His spies and moles don't run into troubles (suspicious guards, delayed flights...) either when they have to infiltrate into the Home Base to performing spying or sabotaging missions.
No Endor Holocaust: Averted. The show has no troubles showing how much death and destruction would cause a humongous war mecha rampaging through the land or a battle between giant robots in a highly-populated city, and often Kouji has to suffer the consequences of it.
No, Mr. Bond, I Expect You to Dine: In a storyline of the Gosaku Ota manga, Baron Ashura kidnaps Kouji Kabuto. Then Ashura treats him like a guest and invites him to have dinner with him to talk him into joining him (Kouji even was provided with a tuxedo). In one moment Ashura asks Kouji if the meal is to his liking and Kouji replies it would be more to his liking if he was not handcuffed. Ashura retorts he is not SO stupid to let him free.
Non-Action Big Bad: Dr. Hell is a certified genius... and a seventy-year-old man who isn't physically fit at all. He always sends his henchmen, minions and war machines off into battle because he can't fight his enemies face-to-face.
No Seat Belts: Depending on the version, this trope was played straight or averted. In the original series Mazinger-Z's seat did not seem having seatbelts, but in Mazinkaiser and other reimaginations you could clearly see Kouji Kabuto strapping his seatbelt before launching.
No Range Like Point-Blank Range: In his battle against Debira X1, the flying Mechanical Beast was too quick for Kouji to hit, so Kouji waited as the Mechanical Beast lunged at him until the robot was at point-blank range to blast it with Mazinger's Breast Fire. Kouji used this tactic sometimes when an enemy was too fast or too sturdy.
Noisy Nature: Subverted in the first episode. Dr. Kabuto's village -where he built the titular Humongous Mecha- was set -in the anime version- in Aokigahara, a forest at the base of Mount Fuji is infamous -among other things- because it is eerily silent due to absence of wildlife. So when Dr. Kabuto heard noises near from his house -not long after his grandson told him that their maid had been murdered-, he knew there were intruders near and his life was in danger.
Not Hyperbole: In the first episode, Dr. Kabuto tells Kouji who pilots Mazinger-Z has the potential to become a god or a devil. Such like later retellings and versions of the history (especially Z-Mazinger or Shin Mazinger Zero) have proved, Dr. Kabuto was *NOT* exaggerating.
Not Drawn to Scale: The applied scale is not consistent at all. There are plenty examples of it: In episode 10, Dian N4 grabbed skyscrappers and moved them to elsewhere with one of his hands, and it seemed to be the same size as the buildings it was carrying. Later, though, the Beast was just as tall as Mazinger-Z (18 meters).
Not What It Looks Like: It happened sometimes in the original series, but Shin Mazinger Zero gave a particularly hilarious example. In a chapter Kouji and Minerva-X are together inside the cockpit. During the battle Mazinger moves a lot and Minerva lands on Kouji on a very awkward and embarassing position (face-down and on top of Kouji, with her head hovering above his groin and Kouji's head stood between her legs). Sayaka -who had just arrived and destroyed three Mechanical Beasts in a fit of jealous rage- sees them, and they -after displaying tremendously comical Oh Crap! stares- try to explain it is not what it looks like, and Minerva was not human but she actually is a Super Robot created by The Professor Dr. Kabuto to be Mazinger-Z's Battle Couple. Sayaka's reaction was an incredulous Flat "What." before trying murdering them.
Nothing Can Stop Us Now!: Baron Ashura tends to utters that sentence in two types of situation: when Big Bad Dr. Hell is showing another of his Robeasts to him/her/it (cue Mazinger Z obliterating the Mechanical Beast twenty minutes later); or when one of his/her/its schemes succeeds or is about of succeeding. Examples of the second use are when a Mechanical Beast has utterly trashed Mazinger Z, when he managed to steal a sample of Alloy Z...
Now, Let Me Carry You: For all times Kouji shouted "You are always getting in the way!", "Stop hindering me!", "I could have won without your help!", etc. to Sayaka there were only so many times where Sayaka had been hurt or her Fem Bot disabled and he carried her back home in arms (one episode closed with a snapshot of Mazinger carrying Aphrodite in arms while they arrived to the Institute). In one ocassion the roles also were reversed in one ocasion where Sayaka carried Kouji.
Now or Never Kiss: In the manga version of the "Mazinger-Z vs Great General of Darkness" movie, Sayaka kisses Kouji right before he goes off to fight the Mykene army because both think he'll die this time for sure.
Nuclear Weapons Taboo: Curiously, it was averted. In the episode 36 it was clearly stated Dr. Hell was fabricating nukes, and a nuclear missile was detonated, even. And in another episode, he placed several nukes in the pool where Mazinger was launched from.
Obviously Evil: During his time overseeing a research team, despite his blue skin and "somewhat telling name", the scientists didn't seem to suspect Dr. Hell might just be evil.
Offscreen Villain Dark Matter: Dr. Hell has the resources to build over one hundred Kikaijuu, two Super Villain Lairs, several fortresses and war machines, and he has an infinite supply of Mooks. It was explained on a chapter of one of the manga versions Count Brocken -one of his Co-Dragons- had taken over several European crime organizations long before the beginning of the manga and was using their resources to fund Hell's operation. And regarding how Hell has an endless army of Mooks... It was justified, but the answer is pure Nightmare Fuel: All his subordinates are corpses he has turned into Cyborgs personally. Often they were people he or his subordinates had slain. Hence, he has an infinite supply of soldiers.
Oh Crap!: It is used many times. A memorable one happened when Baron Ashura was relaxing in his/her submarine fortress, feeling safe due to the knowledge of Mazinger-Z could not reach them underwater because it had not been built to swim or dive... when an Iron Mask showed him through one screen Mazinger-Z was swimming towards them.
And in other episode, Ashura kidnapped Aphrodite A and examined it to learn how building a Photon engine. Later, when Mazinger Z broke into his/her base, a short-circuit burnt the computer they were using, destroying what information they had obtained. Ashura's expression was priceless (one of his/her Mooks got to drag him/her away because he kept staring and gaping at the ruined computer).
A considerably more tragic happens when Prof. Yumi and Prof. Gordon are arguing about a Mechanical Beast is sinking ships... and then Prof. Gordon realizes his wife and their daughter are traveling to Japan by sea.
Oh, No... Not Again!: Boss's robot (Boss Borot) gets wrecked nearly each episode, so often Boss utters one sentence along the lines of "Why it is always me?", or "Not again!". He even lampshades it in one UFO Robo Grendizer manga chapter: He is going to fight Great Mazinger (long story), and he is knocked down with a mere backhand. Then he says "The most painful thing is I knew what this would happen."
Old-School Dogfight: Dog fights happened often between Mazinger-Z and other giant robots, although Kouji also used his mini-ship to try to take some Robeasts down, placing behind them and shooting his missiles. His first real aerial battle -in episode 34- consisted entirely of him and Genocyder F9 dog-fighting.
Once per Episode: Every episode Kouji shouted "Pilder On!" and "Mazin Go!" to dock in its Humongous Mecha and activate it. In some episodes he shouted it even more times if he had to sortie often.
One of the Boys: Sayaka. She prefered hanging out with boys rather girls, and she liked bikes right her male friends.
One-Person Birthday Party: In episode 19, the Small Name, Big EgoButt Monkey Boss tries to get people to purchase tickets to attend his birthday party. However everyone runs away from him, and he can not figure out why. Kouji tries to explain to him that people don't like getting bullied into paying for a party they do not want to go to start with. Finally, Kouji agrees to attend Boss' party out of pity and even performs a couple of tricks with his bike so that more people come. However, during the party, Kouji gets summoned to the Institute, and he leaves. As a result, everybody else leaves too, leaving Boss alone.
Only Sane Man: Prof. Yumi, Boss and Shiro alternated that role in different episodes.
Omnidisciplinary Scientist: Dr. Hell. He could make nearly anything he could imagine, and he dominated multiple fields of science. On the other hand, Dr. Kabuto and his son Kenzo and Professor Yumi subverted the trope, being experts on one specific field and needing help and experts' advice in other matters, and using the trial-and-error method to make scientific breakthroughs.
One-Man Army: It is both played straight and subverted. Mazinger is certainly powerful enough to trash an entire army... but when Kouji has to fight more than two Robeasts at once, he struggles (Mazinger versus Devilman) or loses (Mazinger versus Great General of Darkness, Mazinkaiser...)
O.O.C. Is Serious Business: Tetsuya Tsurugi is serious, grim-looking and moody, and he seldom smiles. So when he grins, everyone freaks out and dons Oh Crap! stares. Mainly Warrior Monsters, since it usually means they are about of dying horribly and painfully.
Our Centaurs Are Different: Kentol Γ7 was a centaur-like, blue Mechanical Beast. It was armed with a spear and a spiked shield, was capable of flying, and its helmet's horns shot beams that could control other machines.
Our Demons Are Different: In the Crossover movie with Devilman showed up the enemies of that series. The demons in Devilman are ancient organisms who can fuse with other living things and inanimate objects to gain many abilities and powers from what they've fused with, taking them over completely. Thus they look like the chimerical creatures from ancient texts. They have psychic powers normally of varying strengths. However, human consciousness is lethal to them. But a person who's scared or otherwise loses control of their higher mental functions can be taken over. Should that person have a pure heart, however...they will posess the demon's flesh and gain their superpowers! And thus was born Devilman!.
Our Dragons Are Different: Several Kikaiju resembled dragons, and the aspect and weapons of each one of them was different: Gelbros J3 looked like a bypedal dragon with three heads could shoot heat waves, soundwaves or acid streams; Drago Omega 1 resembled an Eastern, flying dragon shoot missiles...
Our Giants Are Bigger: In New Mazinger (an one-shot alternate story published in The '80s), an explosion transports Kouji Kabuto to an alternate dimension inhabited by giant beings. The human beings were sixty-foot-tall and just so big as Mazinger-Z (in fact, when Kouji saved one princess, she though Mazinger-Z was an armored knight, and she asked him removing his helmet to see his face). They were mostly good-natured and intelligent, although their technology was at a Middle Ages level, and they were in war against a race of Lizard Folk.
Our Mermaids Are Different: In a story arc of the Gosaku Ota version, a race of giant Fish People from another dimension called Chip Kamoy attempted to invade Earth. In order to communicate with human beings, they kidnapped a human girl and transformed her into a mermaid: her legs were replaced by a long fish tail, and fins grew from her head. She was definitely good, though, and tried to help The Hero Kouji Kabuto. Unfortunately her "masters" executed her in punishment.
Our Hero Is Dead: The "Kabuto Kouji Dies In Lava!" episodes (yes, they did this twice, though the second time was done with tongue firmly planted in cheek) are so infamous for this that they border on Memetic Mutation.