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.
Dr. Rotwang, Mad Scientist extraordinaire who thrives on a Fantastic Racism for the superpowered NEXT. First introduced as a one-shot villain creating robots to take on the heroes, Rotwang appeared in the final episodes as the partner to the Big Bad of the series with one goal on his mind: to wipe out the NEXT and replace them with his robots. Rotwang mocked the very concept of friendship while trying to kill the city of Sternbild's superheroes, calling their friendship and devotion to one another 'pathetic'. Hateful, cruel and genocidal, Rotwang is truly a monster in even the idealistic show.
The Big Bad of the show, Albert Maverick, seemingly the kind and friendly benefactor of superheroes and founder of Hero TV. Maverick was the secret leader of the crime syndicate Ouroboros and was involved in many criminal activities. To make things easier for himself, he presented NEXT as marketable to gain them fans and create a superhero legacy, all the while hiding his being a NEXT himself whose power was Mind Rape. Maverick would murder the parents of future hero Barnaby Brooks to mold the boy into his perfect pawn—rewriting his memories every time Barnaby got too close to the truth. When he realized Barnaby's partner Kotetsu was too close to the truth, Maverick had Barnaby's mother figure Samantha murdered and framed Kotetsu, wiping the memories of everyone who knew his superhero identity. After this failed, he revealed he fully intended to wipe out his own NEXT and replace them with more easily controllable robots created by Rotwang. Feeling nothing but egotistical disgust at the doctor, the second his safety was compromised, Maverick murdered Rotwang after revealing he himself was NEXT.
Counterpart Comparison: Barnaby to Batman; their backstories are quite similar, though their personalities are not.
Keith Goodman has recently been getting compared to Alfred F. Jones/America due to their relatively similar appearances (tall, muscular, blue-eyed blonds) and their personalities (Upbeat, somewhat ditzy Love Freaks).
Jake Martinez is drawing an increasing number of comparisons to the Joker. (Though his younger counterpart must have raided Alan Gabriel's closet.)
Yuri/Scarf-tan thanks to this image◊ from the Hero Awards pamplet.
Ensemble Darkhorse: Biglobe ISP conducted a character popularity survey of most of the shows from the spring 2011 anime season. Behind Kotetsu (1'st place) and Barnaby (2'nd), Sky High was the most popular character in the series...and the entire season.
An in-universe case with Origami Cyclone, who gets a lot of sponsors and a high card sales rate despite placing last in the hero rankings.
There had been plans to kill Rock Bison off, but his surprising popularity in the Japanese fandom meant that the idea was jossed and he ended up getting some extra lines and screen-time.
Epileptic Trees: There have been a few people suggesting Scarf Girl keeps turning up everywhere because she is either the Big Bad, involved with Ouroboros, a Fangirl for the heroes or she's just cursed with awful luck.
Along the same lines, Kotetsu's smartass remark about Lunatic having a glove on his face (and the fandom's subsequent adoption of "Palm-Face" as a Fan Nickname for him) has become a case of Dude, Not Funny! following the revelation in Episode 16 that the design is based on the handprint burn scar on Yuri's face, left there by his father when Yuri burned him to death.
There was a superhero called "Pepsiman" created by Pepsi in the 90s, and here we have a superheroine Blue Rose who advertises Pepsi.
In Episode 8, Kotetsu tells Ivan his power is great because he can just copy what someone looks like and use their power, though Ivan quickly clarifies that it doesn't work that way, he can only copy people's appearances. Later on in the series, Kaede is shown to be able to Power Copy.
Memetic Mutation: For the fans not trying to turn everything Kotetsu and Barnaby say in the end credits into a slash prompt, the main pastime seems to be photoshopping Origami Cyclone into the background of everything.
Similarly, Barnaby wearing five pairs of the same glasses after he mentioned he owns that many in the end credits.
And to go with him, there's Ouro-Bunny - same idea, really - it's Barnaby's evil version, sometimes a Villainous Crossdresser.
Fans have become incredibly preoccupied with fried rice after they learned Barnaby had been practicing making it just for Kotetsu.
After learning that not only Barnaby and Karina, but even his own wife had a tsundere side that was revealed only towards him, the fandom has concluded that Kotetsu has a second NEXT power - drawing out the tsundere in those who're fond of him.
After Episode 19, Maverick. In his case, what doesn't help is the date rape allegory from that episode.
Jake Martinez, whose outfit can charitably be described as looking like a male hooker's. Taking down Origami Cyclone, Sky High, Rock Bison, and Wild Tiger all down in Curb Stomp Battles naturally spawned a lot of rape fanart.
Memetic Sex God: Kotetsu gets a lot of fans very hot under the collar. Pixiv's taken to turning everything he says or does into a metric ton of porn, while 2chan's bought out the entire stock of a brand of cologne◊ simply because they wanted to know what he smelled like. 4chan also joined in soon after.◊ (For added irony, the production team was originally afraid that Kotetsu wouldn't be well received by the audience because the they didn't expect viewers to find him physically attractivenote To quote Ozaki: "Another problem was, as you said... it's been considered that any anime character with facial hair would be a 'bust'. Apparently Japanese women do not feel attracted to men with facial hair.", among other things.)
Moral Event Horizon: For Maverick, it's having Samantha murdered. Of course he actually passed it twenty years ago when he killed Barnaby's parents, but the former is the first time we see his evil side for ourselves.
Narm: Barnaby's breakdown scream in the stinger of Episode 18 is more than a little hard to not laugh at, with facial distortion to rival anything seen in Code Geass.
No Yay: Maverick is really possessive of Barnaby; to the point of drugging him, mind-raping him several times and isolating him in his private mansion. Add in the Power Perversion Potential of having memory-altering NEXT powers and no amount of industrial strength Brain Bleach is ever gonna be enough.
Paranoia Fuel: What Maverick did to Barnaby may serve as this for anyone who has been raised by foster parents. The people who (apparently) loved and cared for you? They're Manipulative Bastards who only ever saw you as a tool to fulfill their own agendas. And while people in real life probably don't have Psychic Powers that enable them to rewrite memories, there are still plenty of ways to manipulate someone ever since childhood.
Real Women Never Have Crushes: A lot of fans react this way to Karina's frequent displays of embarrassment and emotional vulnerability where Kotetsu is concerned, since they see it as an "over-the-top display of her femininity".
Squick: Blue Rose falls in love with Tiger. Not only is he old enough to be her father, but she's only 7 years older than his daughter. Sort of softened in that it's not her first crush on a father figure and it's suggested in side material that she has a general fetish for older men.
While it's up to debate whether Kotesu and Barnaby's English voices are better or worse than their original voices, many of the other heroes and side characters are very well casted and dubbed.
They Wasted a Perfectly Good Plot: Episode 15 features Keith dealing with both a crush and personal insecurities stemming from his drop in the hero rankings. He doesn't get a Kotetsu lecture/pep talk why exactly?
What an Idiot: Maverick's plan to dispose of Kotetsu. It would probably have been easy to call up Ouroboros and arrange a heroic hospitalization, where he could do a memory edit during a visit. Instead he opts for a flashy plan that requires mindwiping everyone who knows Kotetsu's identity and then plastering his name and face all over the news, even though the necessity of the disposal is because his twenty-year edits on Barnaby's memory started failing when exposed to contradicting information. He also forgets that Kotetsu has a family, who could potentially cause the same problem. Not to mention that wiping the name Kotetsu T. Kaburagi from every record everywhere is time-consuming, probably expensive (do men in black suits get paid by the hour?), and could still fail if, say, Antonio had a note in his jacket reminding him to pay Kotetsu back. Also, you're dealing with a hero who was sponsored by a different company before Maverick had him become Barnaby's sidekick and whose HeroTV file (complete with real name) was researched by a judge who, via his anti-hero persona, had confronted him numerous times. It's almost like how a Gambit Roulette would end if it was played out logically.