Anti-Climax Boss: In the Christmas special the man known as "Jesus" might be the most powerful foe the gang have faced. How is he defeated? He uses his psychic powers to pull a cabinet too hard and hits himself in the head. Hoist by His Own Petard. But hey, the gang still won.
Broken Base: After the original cast sold their powers and especially after the complete cast overhaul the entire fanbase was completely split as to whether the show was still good or not.
Nathan stomping on Marnie's afterbirth thinking it was an alien baby who needed to be killed.
"It's the afterbirth, you dickhead!"
And while we're at it, just about everything that comes out of Nathan's mouth besides Carbon Dioxide.
"There's your sperm. So that's awkward."
Darkness-Induced Audience Apathy: Everybody's life sucks from start to finish but it definitely falls into it when, by midway through Series 4, all five originals have departed the series, four of them for unhappy reasons - three die and one ends up in prison, leaving only one to enjoy anything close to a happy life.
Simon's weirdness is toned down after the first series; after that his behaviour evolves into a he's-just-socially-awkward thing but in the first few episodes he genuinely appears to be a little deranged. ("I want to piss on your tits", anyone?) This is because the writers originally intended him to be the villain, but he was unexpectedly popular so they rewrote it, and eventually he is arguably the most heroic and noble character that has ever been on the show.
In the first season, Superhoodie seems to be far too short to be Simon, and gives the impression of being a much younger boy than the other characters. See the Trivia page for more evidence that his eventual identity was a later choice.
Fridge Brilliance: The existence of Psycho!Rudy makes sense when you take a long look at Rudy's behavior: he wet the bed into his late teens, suffers from stifling levels of social awkwardness, deeply suppresses his emotions and traumas, and over the course of the series has shown a distinct lack of empathy, at least when nothing directly effects him.
Fridge Logic: In Series 1 Episode 2, Ruth produces a set of keys, giving the impression that she is a member of staff and has permission to be in the community centre after hours. As it turns out she is actually a client-there is no reason for her to have the keys or to be hanging around the community centre when it is closed. Given that the place has the security of a wet paper bag it's possible that she stole them, but there is no indication that she did or why she would.
In 2.5, when asked why he bothers to try and rescue Simon from danger, Nathan replies: "The little bastard gets under your skin, doesn't he?". A couple of years later, Iwan Rheon, the actor playing Simon, joined the cast of Game of Thrones as Ramsay Snow, Lord Bolton's Ax-Crazybastard son who enjoys flaying people alive.
In an episode of Series 1, Nathan pretends to be Bono from U2, but no one else gets itnote His clue? "I'm an annoying cunt.". Robert Sheehan later appeared in the movie Killing Bono.
Won't be the last timeRobert Sheehan plays a character in a superhero show who can see ghosts. A lot of Nathan's lines, such as calling adopted kids nutjobs and walking around wearing the wedding dress, become a lot funnier after The Umbrella Academy was released.
Nathan and Simon. It starts off as Nathan essentially sexually harassing Simon for shock value, but as their friendship develops, Nathan's teasing seems to evolve into genuine affection. And then there's the episode in which Nathan is mind-controlled into falling genuinely in love with Simon, much to the latter's bemusement, since Nathan's attentions go from obnoxious to sweet and gentle.
Season 3 brings us Rudy and his other self, what with the wrestling and talk of fucking himself. The Season 5 premiere lampshades this, with Rudy Too's attempts to get Rudy One to join a superpower support group sounding like an effort to make him join couples therapy.
Abbey meets a girl at the bar, Laura, who's smell she recognises, making it one of her few memories. She sniffs her a few times, jokes about fucking her with a strap-on, then tells her she's the best smelling person ever.
Season 2 episode 4 could have been easily resolved at any time by Simon turning invisible and killing the Grand Theft Auto guy from ambush.
A good deal of the problems from Seasons one and two could have been quickly and easily resolved with Kelly simply using her mind reading powers, but everyone seems to forget she can do so. Examples include, but are not limited to:
Finding a shapeshifter.
Trying to find out what's causing the strange behavior of their (mind controlled) team mates.
Checking whether their probation worker is the one leaving them threatening notes.
Jerkass Woobie: Nathan, whose jerkassery is largely balanced out by the fact that the writers simply adore placing him in unpleasant situations (though he often has it coming). Essentially, the universe hates him so we don't have to.
Depending on your perspective, the entire second crew can come off like this: aside from Rudy borrowing a lot from Nathan, Finn and Jess are clearly intended to fill the gap left by Simon and Alisha, while Abby was pretty obviously written in to replace Kelly. Alex somewhat gets away with it by being introduced before Curtis leaves the series and having less in common with the character he takes over from, but he's the exception. However, they all eventually grow away from the originals and become rounded characters in their own right, and mostly did gain their share of fans by the end of the series.
Some Anvils Need to Be Dropped: The show takes pains to educate people on what can be considered rape. If you didn't get it when it was implied by Alisha's use of her powers, it was later explicitly called rape by Curtis. Then there was the coach drugging his athletes and even later a very clear statement from Simon to Rudy that having sex with someone who's asleep is rape. Finn also counsels against having sex with very drunk girls.
Nathan and Marnie. He's willing to be her baby's father the same episode where she's introduced just before being Put on a Bus.
Happens with Alisha and Future!Simon. Their relationship is developed over the course of two episodes, Alisha only falls in love with him because he tells her she will, and because he's the only person that can touch her.
Squick: In 3.6 Rudy drops his ice cream upon discovering while urinating what his one night stand did to his nether regions.
Many of the villains can be perceived as this. Most of them were always down on their luck Butt Monkeys before they got their powers, such as Brian the "Milk Guy". He led an incredibly mundane life, then his powers made him famous, then when other people with better powers came along everyone started to ignore him again. Then again, Howard Overman did state in an interview that he tried to avoid creating wholly "good" or "evil" characters, and tried to give all of the antagonists at least some logical motives for the way they behaved. So most of them were probably intended to be somewhat sympathetic.
Simon was originally written as a villain but this was scrapped when the writers realized that viewers liked him.
Unintentionally Unsympathetic: Sally on paper has reasons for her behaviour. She is worried about Tony (they were together) and she suspects something is going on. However the way she goes about finding this out takes away a lot of sympathy from her. Namely manipulating Simon - read: an emotionally vulnerable teenager with a crush on her - and borderline seducing him for information. And she also physically attacks him when he discovers the truth.
Painfully shy and lonely Simon endured years of bullying prior to the show, and still doesn't get off lightly mostly due to his and Nathan's personality clash.
Rudy's literal split personality has this in the introverted one, who admits that Rudy tried to kill himself after he lost his virginity to Alisha and she treated him badly. Later on, his womanizing ways stop and he genuinely falls in love with a sweet, innocent girl who dies.
Curtis loses his athletic career, his girlfriend dies, he gets himself pregnant, his next girlfriend uses him and tries to kill him, then finally he becomes a zombie and shoots himself to save the rest from infection.