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.
YMMV: Batman Beyond
Alas, Poor Villain: Mr. Freeze, as is to be expected, but there's also Earth Mover, Robert Vance, the Terrific Trio, and even Ian Peek.(Seriously, just try not to feel any pity for his fate!)
Angst? What Angst?: In the JLU episode "Epilogue". Terry takes the fact that Waller tried to have his parents killed surprisingly well.
Anti-Climax Boss: The Jokerz. Compared to the rest of the show's Rogues Gallery, they're pretty pathetic antagonists. They're rarely given focus in the majority of the series, and for good reason. Unlike their inspiration, they're just a generic gang of teenage biker punks who bear the Joker's name and face, but none of his truly frightening personality.
Audience Awareness Advantage: Dana gets a lot of flack from some fans for not always forgiving Terry when he misses dates because of Batman duties and making his life difficult, even though as far as she knows, he's just an old man's part-time assistant who's doing a very bad job of balancing his new responsibilities with his prior relationships.
Author's Saving Throw/Character Rerailment: In The New Batman Adventures, Mr. Freeze went on a rampage due to losing his body and Nora, and was going to end it by essentially destroying Gotham. Fans complained about this due to undoing the ending of Subzero, where Freeze finally finds closure, as well as seeming out-of-character. Beyond dials him back, showing him trying to own up to his horrific actions in his sole appearance, but becoming a villain again after one more kick in the gut, and then finally dying, trying to keep Terry from saving his life.
Awesome Music: The series itself has an amazing opening sequence and music in general,
In one episode, Bruce Wayne has to save Terry from Inque. We are treated to a re-orchestrated version of the original Batman Theme during the fight.
One episode featured Bruce and Terry attending a Batman musical. The musical, unfortunately for Bruce, is really campy and almost seems like a musical version of the Adam West series, albeit with the characters in their Batman: The Animated Series clothing. It's hilarious for the fans though, with the purposely-corny numbers having Narm Charm and purposely invoking the So Bad, It's Good trope.
Base Breaker: Max. Fan reactions to her introduction ranged from considering her the best part of the series and thinking she was sold short to considering her the worst character yet and hoping that she'd die and stop taking screentime away from everyone else. Her Base Breaker status also extends to the development team; according to Bruce Timm, some of the writers were unhappy about her inclusion and used Bruce Wayne to voice their own opinions of her, while Alan Burnett at least wanted to promote her toLove Interest.
Complete Monster: Besides The Joker from Batman Beyond: Return of the Joker, the series itself has one in Blight, AKA Derek Powers, a Corrupt Corporate Executive and the Arch-Enemy of Terry. In order to test his latest chemical weapon, Powers purposefully infected Harry Tully, a member of his staff, with it. When Tully leaks the information to Terry’s father, Warren, Powers had Warren murdered to cover it up. Later, Powers sold the weapon to a Kaznian diplomat who wanted to wipe out resistance on his border. To promote his product, Powers showed the diplomat pictures of Tully’s gradual death at the hands of the chemical. Other crimes include committing industrial sabotage, exiling his son, and polluting the ocean by dumping radioactive waste into it. He played a part in Mr. Freeze's tragic demise as well; he used Freeze as a guinea pig to cure his own condition and when Freeze wanted revenge, Blight brutally crippled Freeze with his radiation. He’s also responsible for the creation of the super villain, Shriek, who he hired to assassinate Bruce Wayne for getting in the way of his plans to bulldoze Gotham's historical district for profit. There's also his response to Terry's use of You Killed My Father as a hint to Batman's real identity:
"Do you have the slightest idea how little that narrows it down?"
Contested Sequel: Mostly averted; the series is overall considered a really good sequel to Batman: The Animated Series and has been well-received by the majority of fans. The fact it came out while the previous series was still running, making it a spin-off rather than an actual sequel, probably helped.
Damsel Scrappy: Max Gibson is often considered this by her detractors. This tendency is best displayed in the episode "Final Cut", where she ignores Terry's instructions and snoops around for clues, leading to her getting attacked by an assassin. Terry has to leave his post protecting the assassin's target to rescue her, which results in the target getting mindwiped with a hidden bomb ready to explode thanks to his Dead Man Switch.
The Joker's personal gang of Jokerz, especially Dee Dee, are inordinately popular for only appearing in The Movie. Fans were naturally thrown a bone when Justice League Unlimited went to that time and they were used as Chronos' flunkies.
For someone who only appeared in 3 episodes, Melanie Walker made an exceptionally positive impression on viewers and shippers alike, being one of the most popular romantic alternatives for Terry.
Mad Stan was a one-note villain simply there to force Terry to miss his date with Dana. His outright insaneAx-Crazy personality made him popular among fans and he reappeared in several episodes, finally getting to be the main antagonist when The Zeta Project crossed over. The best part: due to Zeta's naive, cheerful nature, he and Stan actually get along well, resulting in this hilarious line:
Also Inque and Batman. She even kisses him on the mouth to prevent him from relaying a warning to Bruce about her trap for him in one episode.
Fridge Horror: Inque's daughter Deanna never makes an appearance again after "Inqueling". Inque does. And it's a safe bet she wasn't exactly pleased that her daughter tried to kill her. Do the math and you'll probably figure out why we never saw Deanna again...
"Funny Aneurysm" Moment: While going over Presidents with Max, this exchange occurs (This episode was produced in 2000 when the election was going on; then it first aired during the month-long legal battle between George W. Bush and Al Gore, making it even more hilarious.):
Hilarious in Hindsight: Being set in the future tends to attract this from time to time, whether it is Terry quipping "Who reads newspapers anymore?" (in "The Winning Edge") or reviewing the Presidents with "Clinton was the fun one, then came the boring one." (in "Mind Games"). By the time of the series a perfect score is 2400 (see the example in Second Place Is for Losers), which as of 2005 it has been.
In the pilot episode, a Jokerz member says "Let's put a smile on his face," while brandishing a knife. Ever since TDK came out, one may now consider it retroactive fanon that that particular Jokerz member was intentionally quoting one of the signature lines of his "hero."
In "Countdown," Zeta disguises himself as Terry in costume to escape the NSA. Diedrich Bader would later voice a different Batman years later.
During "Disappearing Inque" while interrogating a captured Terry about who Bruce is, Inque asks "Is he your father? Grandfather?" Come an episode of Justice League Unlimited a few years later, we find out Bruce is Terry's father.
And then Robert Vance, or at least the computer program with his memories depending on how you look at it, tries to do the exact same thing to his own grandson.
Nausea Fuel: In "Rebirth Part II", Blight designs a virus that rapidly causes damage to cells in organisms. He shows the effects to one of his allies, first showing a plant utterly disintegrating in seconds due to the effects, and later on a cow and human. We never see the end result but judging by what happened to the plant and how the guy viewing looking ready to vomit, its safe to assume it was a little messy.
The episode "Lost Soul." Just the way the Robert Vance program (or Vance himself, depending on how you look at it) looks on the computer screen with the dead eyes and the ghost-like pallor is Nightmare Fuel by itself. The events of the episode just mix in kerosene with the Nightmare Fuel, and the end where as he's being deleted we hear his memories going back to childhood, ending with the heartbreaking sound of child!Vance asking for his mama just dumps the entire container on and turns it into Nightmare Fuel. There may not be a single episode that can rival how creepy the villain was and how disturbing that end scene was.
Shipping Goggles: Terry/Max shippers sometimes claim that the two are pining for each other or in denial about their romantic feelings, ignoring the time the two were on a date (as part of a case) and Terry even noticed how good-looking Max was, only for Max to completely ignore his notice and nothing else coming of it. When Terry gives Max a chaste peck on the cheek in the comic, shippers cried Ship Tease, ignoring how neither character treated it as at all romantic.
Spiritual Licensee: Batman Beyond is a Spider-Man cartoon. Looking past the Wake Up, Go to School, Save the World premise, Terry is a wisecracking teenage superhero driven by his desire to atone for his past misdeeds and the death of a father figure. He's effectively Peter Parker in the Batsuit. Even the Rogues Gallery is pretty similar to Spidey's. (Inque = Sandman, Spellbinder = Mysterio, Stalker = Kraven, Shriek = Shocker, Blight = Green Goblin, etc.)
Squick: Shriek's creepy little mutant henchman, who likes nothing more than to sit on the floor with a tuning fork that directly stimulates a body's pleasure center. Complete with eyes rolling back and moaning. Who else needs a shower after that?
One of Inque's darker attempts at killing Batman. She puts the squeeze on Terry in order to force his mouth open before shoving herself down his throat in order to suffocate him. After Bruce uses a fire hose to get rid of her, we get a Gory Discretion Shot that saves us from the view of Terry actually puking, but we hear every agonizing heave and see Inque's leftovers spilling onto the ground.
Strangled by the Red String: Terry and Melanie. They met seconds after he got conveniently dumped by Dana, talked a little, kissed under the rain then they're a couple and Mel is unwilling to leave Gotham because of him. Maybe justified by the length of the episode.
They Wasted a Perfectly Good Character: An issue fans took with the series was that several interesting villains were never used for more than three episodes at most before getting dropped for no apparent reason.
Blight was the biggest offender. He was the Big Bad of the first season and set up as the Big Bad of the series period... But nope, he never returned after the first season's finale. The character did reappear in the comics, however — his body survived, but he doesn't seem to remember anything about his past life outside of hatred and a desire for vengeance for Batman and Paxton Powers, and was eventually made into a target for the Stalker, and was eventually killed by being caught in a blast furnace.
Given the number of shippers rooting for her, Melanie may also count as this. For one of the most popular romantic pairings in the show, you'd think she'd appear in more than three episodes. She does appear again in the comics though.
Most of Terry's supporting cast was sorely underused, most prominently his mother Mary, followed by his brother Matt and his girlfriend Dana. For all that they tried to make Terry different from Bruce, they neglected the characters in Terry's life that Bruce could never have had.