These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Broken Base: Between the Mazinger Z / Great Mazinger fans and the ones from Grendizer anime (especially fans from France, Canada and the Middle East for the latter) This is due to the distribution of the anime in this countries previously to the two prequels, leading to the confusion that the former series were actually rip-offs of Grendizer. Besides clarifications over time, there is still a feel of mutual hate, since the anime version of Grendizer differs very much from the original manga and the concept of the whole Mazinger saga, leading over time to Mazinger fans call Mazinkaiser as the true third series from the saga, and Grendizer fans considering their anime as a self-contained universe, somehow settling the conflict (except if a Mazinkaiser vs. Grendizer in Super Robot Wars multiverse turns up...)
Ear Worm: The Italian theme song. GOOOLLLDRAAAKKE!!!
Gateway Series: In France. Arrived in the late 70s on a public channel and created a public outcry. The reason was the french opening song, that some found kinda xenophobic, extending this to the show itself. Was a HUGE success anyway, and it's basically thanks to this show that the anime fanbase exists in France, since it created the first french generation of anime-fans.
Many Middle Eastern anime fans name this as their very first anime.
Germans Love David Hasselhoff: Grendizer has a huge following in the Arab world, as well as in Europe, mostly in the French-speaking parts of both; also in Quebec province.
Hilarious in Hindsight: Naming the enemies "Vegans". So living on an herbivorous diet ruins planets and turns you into destroyer of worlds? They might be trying to imply that the enemies are from the star Vega, but still...
To double the hilarity, Scott Pilgrim features people who gain super-powers by becoming vegans. Countdown to Scott Pilgrim/Grendizer fanfic begins now...
Ho Yay: Shockingly, a section of the fandom sees the relationship between Kouji and Duke like this. Despite having not evidence for it.
Shockingly? Puh-lease. We have two handsome men who are good friends and rivals — it'd be odder if some parts of the fandom did not latch onto this.
Marty Stu: Duke Fleed, unfortunately, is perceived by quite a few to be a good example of this.
Duke: "And it was then... That cruel rain began to fall! A deluge from children began to rain upon Fleed. From three-thousand meters in the sky... The children..."
Sequel Displacement: Grendizer was aired in France before Mazinger Z, becoming fenomenally 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 (Sayaka has always been his Official Couple or at the very least Implied Love Interest, but you talk about facts to a shipper) and he paid more attention to any other woman that showed up in the series (Misato, Erika, Minerva...). Kouji/Maria are the largest faction of the second group by far, due to the sheer amount of people watched Grendizer first. 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.
They Wasted A Perfectly Good Character: Arguably, several of the one-shot Vegan ambassadors/officers, which could have added some interesting complications to the war (Rubina being the worst offender in this regard).
The Woobie: Honestly, Rubina could not catch a break.