Livewire. Now, the main view is that she's a belligerent mean-spirited bigot who became a supervillain and she has no right to be angry with Superman, having "saved her life after all." However, her last facial expression conveys the emotional expression of someone anticipating, with glee, a lethal event. And not only did Superman steal that from her, he ultimately robbed her of her biological humanity. Of course, it was her own stupidity that got her there in the first place...
Relating to Professor Emil Hamilton and his Face–Heel Turn in Justice League Unlimited, after feeling "betrayed" by Superman in the finale, one has to wonder if Hamilton was always a narcissistic Bitch in Sheep's Clothing who took too much pride in being Superman's personal Mr. Wizard ally, or if he was a genuinely good man who sadly never overcame the trauma of seeing just how destructive and dangerous Superman could be if he were evil or brainwashed into being evil. If the latter, did he really join CADMUS in JLU of his own free will or was he manipulated by Lex Luthor and Amanda Waller for their own ends? If the latter, does that make him a victim as well as a villain?
Angst? What Angst?: For someone who came out of cryosleep (which for her would be like going to sleep and suddenly waking up) and finding out the rest of her family is dead, her world is now a complete lifeless husk, and she's been trapped on ice for years, Supergirl seems to take things remarkably well. Possibly justified in that what she had to endure before was like hell and living with Martha & Jonathan Kent on the Kent Farm in Smallville (plus superpowers) must seem like heaven.
Animation Age Ghetto: Most of the series was made to the producers satisfaction, but they were forced to change Supergirl's introductory episode (See What Could Have Been on the trivia page) and obscure Maggie Sawyer's sexuality (See Hide Your Lesbians on the main page) because they were deemed inappropriate for a children's show.
Base-Breaking Character: Livewire. Bruce Timm said in an interview that he and the guys hoped fans would embrace her as "the Harley Quinn" of Superman's series and, while she has some fans and did eventually get added to the comics (even becoming a member of the Superman Family for a while), Livewire was never as popular or well liked as Harley, seeing as how she had none of the tragic sympathy that made Harley endearing; she tended to be more obnoxious than funny, and she gained her powers from, quite frankly, being a complete idiot and blamed Superman when he, you know, saved her life from being a complete idiot.
Broken Base: The 'Legacy' two part series finale. Was it an awesome, emotional, action packed, bittersweet finale to the series or was it a rushed, sloppily written mess filled with plot holes and firm grasps on the Idiot Ball that shouldn't have been made as the finale? While most lean towards the former point of view, the latter has gained popularity in recent years.
While not quite to the extent of Kevin Conroy and Mark Hamill (as Batman and Joker, respectively), Clancy Brown is often seen as having one of the definitive interpretations of Lex Luthor, perfectly mixing a fierce thuggishness with haughty megalomania.
The same counts for Dana Delany as Lois Lane, particularly because Delany has regularly voiced Lois over the years, and her voice-acting handles Lois' snark incredibly well.
And then you have Michael Ironside as Darkseid, whose even, diabolical take is often considered to be the definitive iteration of the character. It helps that he has some of the series' greatest lines.
"Girl's Night Out", the episode of the DC Animated Universe featuring Batgirl and Supergirl against Poison Ivy, Harley Quinn, and Livewire is commonly thought to be a STAS episode, but in reality it is officially a Batman: The Animated Series episode, according to both the episode list on the official website and the fact that it was on the BTAS Volume 4 DVD rather than Volume 3 of STAS (which included the last third of the series, including Supergirl's debut).
"Knight Time" (where Superman teams up with Robin to find out what happened to a missing Batman, even impersonating him briefly) is similarly confused as a BTAS episode.
Darkseid, who later appeared in Justice League and was the top threat of the entire DCAU, is the Evil Overlord of the wasteland planet Apokolips, and ultimately desired total dominion over all life in the universe. To achieve this end, he forever seeks the cosmic power of the Anti-Life Equation to use as the ultimate weapon. Incapable of love or empathy, he abused his loyal son Kalibak, handed over his adopted son Scott Free to be tortured and brainwashed by Granny Goodness, and attempted to murder his other son, Orion, for opposing him. His servants are likewise subjected to torture or death should they fail him, or even question him. Setting his sights on conquering Earth, Darkseid launched a full-scale invasion on the planet, only relenting when the planet was declared off-limits by Apokolips' sister planet, New Genesis. To compensate, Darkseid murdered Dan Turpin solely to spite Superman. He would make numerous more attempts to conquer or annihilate the planet, including attempting to destroy it with an asteroid and brainwashing Superman into leading an attack on his adopted world, turning the Man of Steel into a pariah for years. He later attempted to use Brainiac's programming to collect the Anti-Life Equation and bend the universe to his will, leading to his death in a battle with Superman. Upon his resurrection, Darkseid immediately launched another invasion on Earth, not out of a desire for power, but solely to make Superman suffer. Ruthless and tyrannical, Darkseid is Superman's greatest enemy, and one of the few villains he has outright tried to kill.
Brainiac, who also appeared in Justice League as a threat surpassed only by Darkseid, is a robotic psychopath and collector of data who views himself as superior to all organic life. Once the supercomputer responsible for running Krypton's day-to-day affairs, Brainiac lied to the Council of Elders about the planet's impending doom, prioritizing saving himself over preserving the lives of his creators. Escaping into space, Brainiac roams from world-to-world, assembling all of a planet's information, and then destroying the original in order to increase the value of his stolen memories; his objective is to repeat the process across the universe until he has "destroyed all of creation". Along the way, he murders the crew of a spaceship that was investigating his presence, tries to steal Superman's body for himself, and eventually, after fusing with Lex Luthor, tries to wipe out the entire universe in one fell swoop, aiming to rebuild it in his own image. Void of remorse, and possessed of a bodycount in the billions, Brainiac cared for nothing but his own survival, and his mission of bringing about "the end of all things."
The second episode has a passenger plane hit with a missile and nearly crash into Metropolis. To make it worse the missile was fired by a terroristnote okay so they're more like mercenaries, but everyone called them terrorists in the episode. Similarly, the first part of "The World's Finest" has a scene where terrorists take over Air Force One.
The finale of "World's Finest" has the Joker firing missiles on multiple buildings, sending them crashing to the ground.
In the same episode, Martha wants to give Clark and Lana some alone time so they can talk. So she tells Jonathan that The Dukes of Hazzard is on. And who plays Jonathan Kent a couple years later in Smallville? John Schneider, of course.
Another Smallville-related one in the same episode: young Clark informs Lana Lang about how he is seeing through things; she asks if he's looked towards the girls' locker room. This ended up becoming Hilarious in Hindsight just five years later, when in the Smallville episode "X-Ray", Clark discovers his x-ray vision by accident and ends up inadvertently seeing into the girls' locker room... directly at Lana.
In "Knight Time", Brainiac's line to Superman disguised as Batman, "You are every bit the detective your followers on the Internet believe.", has gotten funnier in light of the rise of social media sites like Twitter and Facebook and their copious use of the Memetic Badass trope.
At one point, Superman complains that he isn't used to all the sneaking around that comes with impersonating Batman. Robin then responds by saying all the stealth is "half the fun". It seems that someone over at Rocksteady had the same idea.
The first episode's ending of Superman simply staring at Luthor who becomes enraged at his silence is very similar to the ending of Lex Luthor: Man of Steel released nearly a decade later.
A female Guardian (seemingly head of the council) appears in the episode "In Brightest Day...".
In the episode "Bizarro's World" a nuclear missile detonates a few miles above Metropolis. A few months later, in "Apokolips... Now!, Part 1", a nuclear power plant melts down just off the coast. To put it mildly, the cancer rate in Metropolis is about to become... impressive.
Don't forget the Joker's rampage in "World's Finest". He blew up quite a few buildings before he was taken down.
Really, everything Darkseid does is this he gives weapons to Intergang that cause considerable damage to Metropolis, attempts an Class-4 Apocalypse How on Earth, and later a Class 5 by crashing a comet into it to wipe it out without breaking his treaty with New Genesis, and in the finale brainwashes Superman and turns him against Earth.
In Parasite's debut episode, when he starts absorbing Superman's energy right in front of a crowd a female bystander watching screams "Good Heavens" in a Dull Surprise manner, coming off as a little silly in an otherwise serious scene.
"Prototype" has the infamous moment where Superman is temporarily blinded by the insane Sergeant Mills, leading to a bunch of sporadic piano music to start playing, but instead of coming off as creepy, it's unintentionally hilarious - as is the way Superman gets smacked around by Mills while blinded.
Superman's Roaring Rampage of Revenge on Apokolips in Legacy comes to an unintentionally hilarious halt when the Furies appear and Superman actually tries to ignore them after he got done killing a bunch of Parademons with his heat vision, so they just attack him anyway and he actually lets them cling to him as they try to kill him and he continues to allow them to go on attacking him until he just crashes into a nearby statue. His encounter with Granny Goodness is also pretty bad and ends up not being as chilling as it was meant to be. TV censorship at its worst.
The Scrappy: Considering the way he thought Superman "betrayed" him in the finale and his subsequent Face–Heel Turn in Justice League Unlimited, it's highly doubtful you'll find someone who likes Professor Hamilton ever again. Bruce Timm stated in his Modern Masters book that THEY didn't like Professor Hamilton in the first place. That's why, when debating who Darkseid should kill, they finally came up with Dan Turpin because they weren't allowed to kill Ma and Pa Kent and they felt if they killed Professor Hamilton, it wouldn't have any impact, because they never liked him anyway.
Squick: In "The Main Man," Lobo defeats a giant snakelike creature by ripping its skin clean off its body, exposing the pulsating veins underneath.
They Wasted a Perfectly Good Character: Volcana; introduced as an Anti-Villain with a sympathetic motivation, who had interesting interactions with Superman. All of this is only explored in her debut episode, and all her appearances after that in the DCU depict her as a straight villain who only cameos.
Lois Lane in "Target". She's put herself in danger multiple times, but at least usually she didn't know how dangerous it was or at least tried to take some kind of precaution. Here she knows exactly how dangerous her unknown enemy is and she's actually has police protection. During a phone conversation with Clark she suddenly realizes who's trying to kill her. What does she do? She sneaks off to confront them face to face. While Clark and everyone else still thinks she's under police protection. If it hadn't been for Luthor just happening to call Clark to give him a vital piece of information, she would have been dead by the end of the episode.
In "The Main Man," Lois goes after Lobo with a metal pipe... after she's already seen him shrug off multiple punches from Superman.
Pre-Livewire Leslie Willis for thinking it was a good idea to hold a gathering of her fans in the middle of a storm. Look where that got her...
The Janitor who hands his Walkman headphones to Livewire in "Double Dose." There's a "No Electronics" rule for a reason, pal. For that matter, the security guard who takes said janitor's watch, but fails to also collect the Walkman. How do you miss that?