Hal and Kilowog in "Reboot". Their hostility against LANOS begins immediately, without context, and they're willing to replace his AI with Aya's when the latter is to be dissected. This winds up as a Double Standard since it sends the message that it's okay to trade one sapient entity for another so long as the other is a Replacement Scrappy.
Anti-Climax Boss: After the Anti-Monitor being built up as a genocidal, universe-crushing, unstoppable Big Bad from the moment he appeared onscreen, he's killed by a super-charged, emotionless Aya in a matter of seconds before she hijacks his body and takes over as Big Bad of the season.
Awesome Music: The soundtrack overall is gorgeous, and the title theme sure makes for its short run time with a triumphant fanfare.
Broken Base: The relationship between Aya and Razer. Is it a moving romance that became one of the best parts of the show, or a creepy Romantic Plot Tumor that was ultimately pointless thanks to Aya's death in the final.
Complete Monster: Atrocitus, the Big Bad of the first half of the series, is dedicated to the destruction of the Green Lantern Corps, having many of them murdered by his Red Lantern followers. First showing his ruthlessness in ordering a colony world full of innocent civilians destroyed, Atrocitus later revealed he had destroyed worlds to fill survivors with rage and recruit them as Red Lanterns. Unlike his comics counterpart, a Tragic Villain at worst and an Anti-Hero at best, Atrocitus in the show delighted over the pain he caused innocents and took sadistic pleasure in his actions. Even though he himself had once lost a homeworld, he gloated over inflicting the same agony on others like Razer.
Even when his only appearance was a few seconds in a sizzle reel, fans adore Saint Walker. This became ever more apparent when he appeared in the show came off about seventeen times more badass then he's ever been in the comics while keeping his characterization completely intact.
Ch'p. Within seconds he proved himself capable of taking out Hal Jordan, despite said Lantern's greater experience and having gone toe-to-toe with Atrocitus. It also helps that he's a squirrel.
The Steam Lantern is getting a lot of love too.
Fanon: There's a creator-supported theory that Razer has white hair.
When Aya is drawn as an organic being she's always drawn with a white Bob Haircut.
The thrill that the planet from the Steam universe feels when they see the stars again becomes this when the stars start going out in their new one too.
The hashtag for the Twitter storm for the episode "Dark Matter" was "#HeroesNeverDie". Aya does.
Well there's no proof that Aya died or not so if this had a second season that may have been true
"Dark Matter" opens with a speech from Appa Ali Apsa giving a speech to the Green Lanterns, saying that these may be the very last orders he will give them. In light of the series' cancellation, this provides a bit of Reality Subtext.
Ho Yay: In "Lost Planet", Drusa comments on the perfection of the curvy Aya and even gives a Male Gaze to her. She even pretends to twist her leg to have her carry her to the ship (granted she was just hacking into the ship but all the signs were there).
Internet Backdraft: News that the show would be cancelled did NOT go over well. Giancarlo Volpe wasn't particularly happy about the decision either. Even worse is that the network had let them know this for a long time but had refused them permission to say this until it was publicly announced. The internet then tried rallying to get the show restored, seemingly failing.
To an extent, Larfleeze. Yes, he is a greedy jerk, but you can't help but feel sorry for him when you see him bursting in tears, crying to get his "shiny" back. Becomes even sadder in perspective when you realize this guy once fought toe-to-toe with Atrocitus.
Just Here for Godzilla: A large amount of people only watched the show for Razaya, and the fanbase often ignore the other characters in favour of them. It isn't helped by the fact that they were the only ones to get any significant character development.
Squick: Aya taking on the form of Razer's dead love and eventually starting a romance with him while still using it. She does it innocently, but it's still uncomfortable for some and is a contributing factor in their romance being polarizaring.
Strawman Has a Point: Kilowog's arguments against Aya being a Green Lantern. While many of them boil down to "she's a machine" and cannot qualifynote he doesn't bring up the Guardians having a say in it, but then again the Guardians are the poster children for counterproductive, that and in Season 2 the Science Director tried to have her disassembled.. However, some points, like her assuming a robotic form and leaving most/all the systems of the ship, hold water, like when she left it to the cargo captain, who accidentally detached the cables she was using to tow a ship, and he could have flown it into the black hole. Also, when Razer caused an explosion/virus, she could not see what he was doing to the ship's systems from her form, and only used an optic to see what he was doing it was a fake out, but if it wasn't they'd be stranded right behind Shard.
The Anti-Monitor is widely regarded as one of the most powerful villains of the DC Universe, having wiped most of the multiverse in the mainstream and while he's presented as powerful and menacing... He's taken out by Aya, who takes over his body as the "Aya-Monitor" and when it turns out he's alive he gets his head smashed.
Tomar-Re could have become the Sixth Ranger of Hal's group, considering his role as a more by the book lantern and was more level headed than the others, instead he only appears in 3 episodes.
Additionally, when the whole Green Lantern Corps ends up fighting the Manhunters, we see neither Sinestro (who was in for one episode and that was it, we probably would have seen more had the series continued) nor Mogo (who had appeared before and probably was banned owing to Story-Breaker Power).
Uncanny Valley: Aya's face/eyes may fall into this category, depending on the viewer.
Invoked when Aya inhabits a decaying Manhunter's body. Everything from her face to her very movements is extremely unsettling.
What an Idiot: Yeah, go on, Ragnar, kill a Green Lantern in order to become one. His ring will surely judge you worthy for that... Even worse is that Ragnar is a fan of the Green Lanterns (meaning he should know that), yet he only believes that brute strength and ambition makes the wearer worthy, if that was the case, it still wouldn't go to him. Furthermore, even if Ragnar found a way to overcome this, the Guardians would never allow a power ring to be hijacked like that and the villain would face as many Green Lanterns as it takes to confiscate it.
Sure, Scar. Trying to take on the Anti-Monitor single handedly will surely end well.