Many fans treat Kouji Kabuto as an arrogant, sexist Jerk with a Heart of Gold and a Chaste Hero based on the first anime series, in spite of later retellings and remakes mostly based on his original manga incarnation where he was less of a sexist toward Sayaka and less of a jerk, being nicer and tactful, yet also more of a pervert as befitting a Go Nagai creation.
Some fans think Sayaka Yumi is stuck-up, bratty and more interested in showing off than saving the world, whereas other fans state she was simply an Action Girl who had very little patience with a loud-mouthed Idiot Hero, as well as an aloof father who cared for her but was Married to the Job.
The interpretation of the relationship between Kouji and Sayaka also varies depending on the fan. Many consider them matter-of-factly the Official Couple, but some argue Kouji did not love Sayaka back, basing that interpretation on him teasing and mocking Sayaka constantly and showing interest towards any girl but Sayaka (Hitomi, Misato, Erika... even Minerva-X) and his being nicer to Maria in UFO Robo Grendizer. The former group of fans are quick to point out that:
Most shows used the Chaste Hero trope back then— The Hero is too busy saving the world to get too concerned about romance;
Kouji baited Sayaka because he was a sexist jerk and not because he was uninterested in her. Belligerent Sexual Tension was an Unbuilt Trope back then: the anime series showed plenty of moments where Kouji cared for Sayaka, the Go Nagai manga made it way more obvious he liked Sayaka, and in the Gosaku Ota manga they do kiss.
Kouji was more mature when he met Maria (when the first series began he was sixteen. In Grendizer he was already nineteen) and she was supposed to fill Sayaka's role.
And let's not get started with the ones think there was Ho Yay between Duke Fleed and him...
Boss is the Plucky Comic Relief to some fans. To other fans he is an unsung hero who always helps the main characters and gets nothing for his efforts despite some of his actions contributing to save the world. And depending who you talk to, he played straight or subverted the Hopeless Suitor and Stalker with a Crush with Sayaka.
Dr. Hell is a Large Ham who wanted to Take Over the World to force the whole humankind to bow down to him, but in Shin Mazinger he was actually trying to save the world (although he thought conquering it was the proper way to accomplish that). Some fans actually feel Sympathy for the Devil, thinking it was unfair he worked so hard, scheming complex plans and strategies and crafting incredible scientific breakthroughs only to be defeated, crushed and humiliated over and over and over by a loud-mouthed, Jerkass Idiot Hero with a cool Humongous Mecha. People who know about his Backstory also tends to see him as The Woobie.
Yuri, Sayaka's Bratty Half-Pint cousin, is regarded by some fans as an insufferable, unbearable brat. Other fans see her as The Woobie, a poor little girl yearning for attention because her parents neglect her constantly.
Cargo Ship: A mind-screwing example, overlapping with Robo Ship. Minerva-X was a Fem Bot was programmed to be Mazinger-Z's Battle Couple. So she was in love with it. However, she also was a Humongous Mecha, only unlike Mazinger she was sentient, had her own mind and could feel, think and act on her own. Sayaka declaring only herFem Bot Aphrodite-A was Mazinger-Z's true Battle Couple partner did not help matters...
Cry for the Devil: Neither the original manga penned by Go Nagai nor the anime series went into the past and motivations of the villains. The manga penned by Gosaku Ota and published simultaneously with the tv show finally revealed what they were. In one of the last chapters, as Dr. Hell is making preparations for the Final Battle, Dr. Hell begins to narrate what his early life was like. We learn during the flashback that he was born in a very poor family. His mother never wanted to have a child, constantly stated his existence was a bother for her and beat him constantly as his father did nothing. No child wanted to play with him because he looked ugly and weird. Looking for a way out of it he turned to books. He became very intelligent, began to get excellent grades in school... and then his teachers accused him of cheating and several of his classmates bullied him. He grew up without friends until he got to college, when he befriended someone who appreciated his intelligence and he fell in love with an exchange student. Shortly after he found out they were a couple and his frayed mind was already so paranoid he thought they were plotting against him to backstab him. After another unpleasant incident where he got beaten for a good deed (a little girl slipped in front of him and he caught her, avoiding she hit the ground and got hurt. It was a well-meaning, innocent act. However her parents thought he was molesting her, and her father pummeled him) his mind finally snapped and he decided Humans Are Bastards and one day he would wipe the world of idiots and everyone would have to kneel before him.
Do Not Do This Cool Thing: Throughout the entire Mazinger trilogy and alternateseriesGo Nagai tried to send the message of War Is Hell. Cities were destroyed and burnt to ashes, innocent people were hurt and suffered, died in horrible ways (there are several instances of genocide), lost their loved ones, were enslaved or brainwashed... and victory always had a high prize. Unfortunately, he did so by showing really cool battles between colorful and awesome Humongous Mechas and impressive, imaginative monsters duking it out with spectacular Weapons Of Mass Destruction, so a lot of viewers kind of missed the point.
In a meta sense. Go Nagai originally made this simply to blow off steam while writing the horribly depressingDevilman manga and directing the anime. Mazinger blew Devilman out of the water in terms of popularity, which Nagai always had odd feelings about.
Boss, the resident Joke Character, is extremely popular with the fandom.
Even the remakes (Mazinkaiser, Shin Mazinger, Shin Mazinger Zero) tend to focus on the Mazinger Z era, as Kouji gets put front and center while his successor protagonists Tetsuya of Great Mazinger and Duke Fleed of Grendizer are sidelined or completely ignored.
Harsher in Hindsight: In episode 17, Holzon V3 unleashed a chain of strong earthquakes which left several Japanese cities in ruins and killed a lot of people. In the wake of Fukushima, that episode looks even more tragic.
And Dr. Kabuto's manor, where he built Mazinger-Z, was located on the Forest of Aokigahara. Why is that relevant? Read and get creeped out. At least it seems clear why Juuzo chose that place: nobody would try to bother him or spy on him.
Also, the name Mazinger is similar enough to the name of pope Benedict XVI/Josef Ratzinger, that it lead to a flood of jokes. [http://nonciclopedia.wikia.com/wiki/Papa_Mazinga]. Especially the film title "Mazinger vs Devilman" becomes extremely hilarious in that context.
Jerkass Woobie: Dr. Hell. His parents were poor and his mother abused him constantly when he was a little kid, calling him ugly, telling she had never wanted to having him and her life would be easier without him, beating the crap out of him for anything while his father shrugged and ignored it. No child wanted to befriend him either, telling him he was ugly and weird. He found a getaway in reading books and started getting exceptionally good grades in school, but the only thing that accomplished was his teachers accusing him of cheating and giving his schoolmates an excuse to bully him. It went From Bad to Worse when he grew up. He fell in love with a woman but then he found out she was in love with one of the only people who had shown him respect (neither of them had wanted to hurt him, but his sanity was already so frayed he genuinely believed they had pretended to be his friends to backstab him).
The legendary HK subtitles are a goldmine of these. Outside of the aforementioned "we are entering the age of Fatso", gems include "don't be a cockhorse", "I AM MAKING THINKING NOISES HERE", and referring to Dr Hell's scepter as the Crabstick.
"Increase the soup." This was another infamous bootleg translation line, this time from Baron Ashura. Tumblr loves this one.
Nausea Fuel: The Mazinger series, being made by Go Nagai, have plenty of this, although compared with works like Devilman, Nagai toned it down:
Mazinger Z: In one of the first manga chapters, Kouji knocked an Iron Mask's helmet down during a fight, and then saw his brain was visible underneath (with tubes and circuitry sticking out of the brain matter). Shortly after, when that Iron Mask attacked him, Kouji accidentally slit his throat, and a gush of blood splashed him.
Later, when he was fighting the Gamiasisters, he chopped them into pieces. They were so human-like they bled as he did so, and their remains lying on the floor looked convincingly like dismembered, blood-stained humans corpses (as Kouji noted, trying not retching).
Great Mazinger: One of the manga versions gave us a delightful panel where Marquisse Janus bisected secondary character Misato lengthwise with one single nail of her Humongous Mecha.
UFO Robo Grendizer: The scenes of the Fleedian genocide in the manga. Along with the visions of charred corpses, there is a particularly brutal flashback where one of the Vegan commanders lets drop hundreds of people (including children) from several thousands of meters of height. Some panels showed heads of people splattering upon hitting the ground. Duke Fleed described the scene as "a deluge of children falling from the sky".
Shin Mazinger Zero: Where to begin? In the first arc you have Kouji getting his arm ripped off and Sayaka getting raped and then impaled with several dozens of metal rods. In the next arc, the Gamia triplets shredded two guards to thin ribbons. Shortly after that, another guard got shot through her skull and then sliced in half, and the third got cut in half when she tried to run away...
Nightmare Retardant: Count Brocken's appearance— a man whose head and body are split apart, with the former constantly hovering around the later, talking, laughing and screaming— was meant be frightening (in the manga he got Kouji reaaaly scared when he showed up for first time, and in the anime Baron Ashura initially thought it a bodyless ghost). Buuuut in the manga Boss managed to grab his head when he got distracted, and Kouji and his friends played keep-away and Brocken Ball (soccer with Brocken's head: the only rule is everyone wins— except Brocken). It was a tad hard taking him seriously after that. That scene did not happen in the anime, but on the other hand you had Brocken's head and body arguing with themselves— and the body punching the head— or Ashura grabbing his head and slapping it around...
OT3: There are not many fans who do this, but some of them consider Kouji/Sayaka/Maria is a solution to the most important Love Triangle in the trilogy (nobody seems considering Kouji/Sayaka/Boss or Tetsuya/Jun/Boss, nevertheless. Poor Boss). It is lampshaded in this Super Robot Wars Yonkoma comic: ◊
Also contrary to popular belief, Mazinger Z was not actually the first anime and manga series to introduce Rocket Punch. The credit actually goes to Mitsuteru Yokoyama's Giant Robo (which came out 5 years before Mazinger Z) for being the Trope Maker for Rocket Punch.
Robo Ship: Minerva-X sees herself and Mazinger-Z like partners.
Sequel Displacement: Grendizer was aired in France before Mazinger-Z, becoming phenomenally popular. When Mazinger-Z was aired, it was accused of ripping-off one of its sequels.
Ship-to-Ship Combat: In this franchise's fandom you find two kind of people: those that think that Kouji Kabuto was in love with Sayaka Yumi, and those that think that he barely cared for her like a friend. And then you have the people who ships Sayaka with Boss, or the arguments among Duke/Hikaru and Duke/Rubina shippers. However, debates between shippers are refreshingly civil and without mud-slinging.
The Gamia sisters were three identical Robot Girls. Outwardly they seemed three ordinary human blonde girls... until you noticed their skin was unusually pale, their motions were eerily mechanical, their expressions were completely aloof and unchanging, they were nearly always silent and they never blinked. Anybody saw them could immediately tell there was something seriously wrong with them... before they began punching holes in walls and shredding things with razor-sharp hair.
Most of the human-looking androids Dr. Hell built were sufficiently well done to reasonably pass for humans. An exception was a Kouji-alike android. That robot looked like Kouji, but it behaved differently and was mute.
Shiro. His parents died when he was barely a toddler. His grandfather Juuzo took them in, but he hired a maid to raise them because he was barely ever home. Several years later, in one single day, Rumi (the maid; he treated her like a a kind of older sister) and his grandfather was murdered (and Juuzo died right in front of his grandsons), and his older brother Kouji nearly stomps him under the foot of an Humongous Mecha. We see during the series he is lonely because he don't have parents to stay with, and Koji, Boss, and Sayaka are usually busy fighting a Mechanical Beast. He had a crush on a cute kid called Lorelei, but she died. And in one of the last episodes, Dr. Hell created a robot that looked like Kouji and Shiro's mother. She managed to convince him she was his real mother and tried to manipulate him to blow up the Jet Scrander. Later he had to shoot her— while still unsure if she was his real mother. Have I mentioned he was only ten when the series began? Later, in ''Great Mazinger', he found out his father was not dead. And he had let his sons believed during years he was dead. And then, shortly after Shiro forgave him and they made up, his father Kenzo died. For real, this time.
Yuri, Sayaka's cousin, was an annnoying, cranky, demanding Bratty Half-Pint. She acted like that because her parents were too Married to the Job to take care of her. Also, she is an Ill Girl in a wheelchair, and she refuses to undergo therapy to walk again because she is afraid everyone will leave her alone again.
Mitsuo, Shiro's schoolmate, was a fat, shy kid wore glasses. Needless to say, bullies targeted him, and he hardly had friends. Shiro scared the bullies away once, but he told Mitsuo he could not help him and be his friend if he did not learn to stand up for himself. All that piled-up abuse was the reason he pulled a Too Dumb to Live stunt.