The Kingpin for a time became better known as a Spider-Man villain, which is fitting since he made his first appearance in The Amazing Spider-Man #50 and was chiefly a Spider-Man villain before being associated with the Daredevil franchise.
The Golden Age heroes from the "Six Forgotten Warriors" arc are best associated with their appearances here due to their comic counterparts from Marvel's Timely Comics era falling into obscurity after 1940s, much like the heroes did in-universe.
Anti-Climax: The "Grand Finale" of Mysterio's act in his debut episode was anything but. With a lethal weapon aimed at him, Spider-man has only one chance to strike the real Mysterio amongst multiple impostor illusions. This could have been suspenseful in a "do or die" way, but the pacing was far too quick to even understand what's going on.
The Kingpin. Some regard him as an effective Big Bad, while others believe that he became far too overused over the course of the series, especially at the expense of other villains.
Mary Jane due to her ugly yellow cardigan, bad coloring on her design, annoying high-pitched voice, and being the source of a notoriousShoot The Shaggy Dog Story involving her falling through a dimensional portal, later coming back and getting married to Peter only for it to be revealed that she's a clone who is then destroyed, and the real Mary Jane is still stuck in dimensional limbo...with the series ending before Peter ever reunites with her.
The quality of episodes after the first season. Some fans think that the show grew the beard after the first season with its story arcs, Character Development, and focus on Peter's personal life, while others think that the show declined in quality, citing bad animation, constantly recycled footage, the overuse of the Kingpin, Morbius or Madame Web and more space and vampire stories.
Christopher Daniel Barnes as Spider-Man. About half the fanbase thinks that he is the definitive voice for Spider-Man, as Kevin Conroy is the definitive voice for Batman. The other half thinks that Barnes was way too melodramatic as Spidey and his voice didn't fit Spidey at all.
Cletus Kasady, aka Carnage, is introduced as an Ax-Crazy lunatic willing to use a bomb to kill himself and everyone within a 200 meter radius just for giggles. After entering into the service of the Dimension Lord Dormammu and bonding with the offspring of Eddie Brock's symbiote, Kasady uses his newfound power and connections to become an even worse menace. Unlike Eddie who, when bonded with his symbiote, creates a combined persona called Venom, Cletus is so psychotic that he still remains completely aware and in control after bonding with his symbiote. First helping Venom steal an interdimensional probe, Kasady quickly displays contempt towards his "dad's" softness and proves himself willing to kill Venom on the flimsiest of pretexts. Kasady would later go on to steal the souls of numerous innocent people in order to summon Dormammu and herald The End of the World as We Know It. Once Spider-Man defeats him by letting him be sucked into Dormammu's home dimension, Kasady attempts to grab Eddie Brock's Love Interest, Dr. Ashley Kafka, to take her with him. He's only thwarted by Eddie sacrificing himself instead. Rampantly homicidal and needlessly sadistic, Kasady was a far cry from the usual Spider-Man villain, doing evil solely for thecarnageit unleashed on the world.
Herbert Landon is a Mad Scientist, the Evil Former Friend of Hank McCoy, and a genocidal Smug Snake driven solely by hatred. A rabid anti-mutant extremist, Landon created a formula that destroyed mutant cells and killed any mutant exposed to it. His endgame was to market this formula to the public as a cure for mutants only to instead use it to wipe them all out. The first person Landon attempted to test out this formula on is his "old friend," Hank. Thwarted in this endeavor, Landon would go on to become The Dragon to the Kingpin, and performed various unsavory deeds such as forcibly converting Alistair Smythe into a cyborg slave and testing out a Super SoldierSuper Serum by using Felicia Hardy as a guinea pig.
Creepy Awesome: Carnage, before and after his transformation, due to his sheer batshit insanity.
This show certainly played a large role in promoting Hobgoblin and Shocker into the limelight. The former being ironic, considering the producer outright hated the Hobgoblin and only included him because of decisions his predecessor made.
Daredevil's solo appearance takes the best bits from his backstory, and distills them into a concise, tightly-written two-parter. His honesty, good nature, sense of humor, and remaining idealistic despite the odds makes him a very likable character. Shame his spinoff series never went off the ground.
J. Jonah Jameson has always been a key figure in Spidey mythos, but the more sympathetic Freudian Excuse he had here for his dislike of Spidey also managed to net him fans. Edward Asner's performance as Jonah is particularly a fan-favorite, which likely played a big part in him also getting cast in futurecartoons starring Spidey.
Fashion-Victim Villain: When "in persona", the Spot appears as a bald human being who is completely white from head to toe, whilst covered in large black spots.
Fight Scene Failure: The show had a number of heavily castrated fight scenes due to heavy censorship refusing to let Spider-Man throw a punch when battling villains. Pretty much all of the fights are done with Spider-Man's webbing. Very rarely you'll see an actual punch in a Wham Episode, such as when the Green Goblin abducts Mary Jane and takes her to a bridge many comics fans recognized...
First Installment Wins: There are fans who see the first season of the show as the one with the most memorable and well-written episodes, like "The Night Of The Lizard" and "The Alien Costume Saga", and with the best animation in the entire series. The following seasons are more divisive.
Gateway Series: For many kids, this was their first exposure to Spider-Man and its mythos. While it certainly took liberties with the comics, the results generally work well, all in all providing a good jumping off point for a fan.
The dissolution of Mary Jane's clone became more of a tearjerker after the release of One More Day, which retconned their marriage in Marvel comics.
An episode of a disfigured former actress plans to kidnap Mary Jane and use a device to transfer her mind into Mary Jane's young and beautiful body it doesn't work as Mysterio tells her that what she wanted was scientifically impossible. In Superior Spider-Man Doc Ock used this trick on Peter... and it worked.
The final episode has Stan Lee remark that Spider-Man isn't the character he used to write anymore, with Spider-Man responding "What can I say? We all have to grow up someday, even we characters of fiction!" This remark stings for many fans in the 2000s and onward who believe that the editors and writers at Marvel refuse to let Peter Parker actually mature and still write him as if he's a teenager, hence things like ending his marriage with Mary Jane.
In the first episode Spidey complains about why he has to crawl around sewers and can't land an easier superhero gig with the Avengers. He also complains about not being "a galaxy hopping superhero," which he essentially becomes in the final episodes.
Among the Spider-Men from alternate universes in the Secret Wars arc, there is one in particular that claims to have taken Doc Ock's Combat Tentacles after defeating him. Almost twenty years later, the Superior Spider-Man debuts.
Then there's pre-vampire Morbius, who looks and sounds kind of like Tommy Wiseau.
This show had the Kingpin being played by a black actor, long before the Daredevil film caused such an uproar by doing it.
Fans of the Black Cat/Spidey ship probably rejoiced when they saw, of all things, Cinderella III: A Twist in Time, which had Jennifer Hale (Black Cat/Felicia) as Cinderella and Christopher Daniel Barnes (Peter/Spider-Man) as the Prince, both of whom in that movie kick ass. (And it was released just two years prior to Disney's acquisition of Marvel for added irony (though technically they had owned this series since 2001- long story involving Freeform).)
This isn't the last time they made a Superman reference.
Iron Woobie: The Scarlet Spider. He's been through all the same trauma that Spider-Carnage has, but somehow came out okay.
J.Jonah Jameson's distrust and dislike of Spidey make much more sense when we learn that his wife was killed by a masked gunman. Alistair Smythe arguably qualifies for this trope, along with Morbius.
The scene where Kingpin's wife leaves him is surprisingly sad and is the one time the Kingpin shows actual remorse for his actions.
Venom. Sure he went off the deep end in his first appearance, but it was motivated by the loss of his job, apartment, and reputation thanks to Peter's unintended actions as a reporter. In his second appearance, it's established he's cooled down quite a bit without the Symbiote. Even when he merges with it again, it's purely out of protection for his girlfriend, and later implied to be from the shared knowledge he gained from Peter. As a result, he gets a very tragic Disney Villain Death.
Morbius was introduced as an arrogant jerk and a romantic rival for Felicia Hardy, and he proceeded to steal Peter's blood in his attempts to get ahead in their 'rivalry,' but the rivalry is because he needs funding to find a cure for a plague afflicting his home country, and he goes through more than enough bad karma by being turned into the TV-Y7 version of a vampire and eventually further mutated into a bat beast right in front of Felicia.
Spidey screaming "SHOOOOOOOOCKERRRRRRRR!!!!!!! YOU CAN'T RUN FROM ME! I'll CHASE YOU TO THE ENDS OF THE EEEEAAAAARTHH."
Spidey's "This is starting to sound like a bad comic book plot!" in the two-part finale was already a Take That! to the Clone Saga in the comics, but has been used often by fans to express dissatisfaction with any bad storytelling in comics, particularly after its usage as a running gag in Atop the Fourth Wall.
Mondegreen: Many people hear the line "Radioactive spider blood" in the theme song as "radioactive spider glider" thanks to the garbled electronic lyrics.
Moral Event Horizon: If Kingpin didn't already cross it by the time Daredevil made his appearance, he certainly did after letting his son be convicted of his own crimes to keep his reputation clean. He justifies this with the coldly-delivered "sacrifices must be made", in essence doing the exact thing his father did to him, without any remorse to speak of.
Especially odd is their treatment of Morbius; any kid knows what vampires do, so who exactly did they think they were protecting? Not only is his hunger for plasma not nearly as threatening as a thirst for blood, but plasma is 90% water, so he could easily get a drink from a water fountain and he'd be fine.
The SHOOOOOOOOCKERRRRRRRR!!!!!!!-line mentioned in Memetic Mutation. It might also fall into Narm Charm seeing how it's actually supposed to be Spidey losing his mental grip and going off the deep end.
The show was pretty infamous for seeking to avoid every variation of "die" or "kill". Sometimes the aversion of the word death would take the dialogue into this territory. In the episode "Return of Hydro-Man, Part II", Mary Jane says, with all seriousness, "I just can't shake the feeling that when we find out what's wrong with me, it's going to lead to my destruction!" Serious intents or not, try saying that out loud and see what kind of reaction you get. This Mary Jane was later revealed to be a clone, and did indeed die shortly later.
After a while a lot of the fights started to look silly due to the fact that censors wouldn't allow Spider-Man to do the kind of knock down drag out fist fighting that superheroes are known for.
Spidey sounding like a an old man with breathing problems as he shakes his fist and yells "YOU'LL PAY OSBOOORNN!".
The much-reused clip of Spider-Man dodging Doc Ock's tentacles in a box-filled warehouse, which even gets trotted out when he's lost his powers, with the show pathetically trying to cover it up by dubbing in the line "At least I still have some of my spider-agility."
The cab drivers from the episode "Attack of the Octobot", especially Mousie. It's mostly due to their annoying voices and the fact that they were all ethnic stereotypes.
Anna Watson, an Obnoxious In-Laws that has nothing but bad things to say about Peter in spite of the fact that Peter was never anything but courteous towards her. It doesn't help that the Anna Watson from the comics was nothing like this.
Take That, Scrappy!: Spidey's tirade against Madame Web matched what many viewers felt about her.
Spider-Man: I am sick of you... and your riddles. And your lessons! And your SUPREME ARROGANCE! Don't you ever, EVER enter my life again! Do you hear me? DO YOU HEAR ME!?
And she didn't, at least until the "Secret Wars" episodes. Which she says she foretold about before leaving.
"The Return of Hydro-Man part 1", Peter finally gets sick of Anna Watson's rudeness to him and rightfully calls her out on accusing him of not caring for Mary Jane.
Unexpected Character: In the Series Finale, Spidey went to an alternate universe where he met Gwen Stacy, who was unexpected because there was no appearance or even mention of any Gwen Stacy in that series until then.
Spider-Man:(thought) Great, Parker, you're engaged to a girl you never even met.
Unintentionally Unsympathetic: Harry Osborn doesn't come off too well in this show. He's meant to be a Jerkass Woobie as per usual, but he gives into evil and insanity way too quickly in "Return of the Green Goblin". It doesn't help that in the season before this, he acted spiteful toward Peter for "stealing Mary Jane" from him, as if she was an object he had ownership of, ignoring the fact that MJ broke up with him and then got together with Peter by her own free will without Peter having done anything. And then when he learns that Peter and MJ are getting married while he's getting psychiatric help, he willingly accepts the Green Goblin's help, crashes the wedding, and threatens to blow up the churchif MJ doesn't marry him instead.
The Untwist: The identity of the Hobgoblin, thanks to Mark Hamill's distinctive voice. Even the credits didn't try to hide it!
Villain Decay: Many of the villains within the course of the show suffered this. Most glaring would be:
Dr Octopus, who became a mere flunky for the Kingpin, even giving up on his plans to become The Starscream shortly after the time he got defeated by a child.
Hobgoblin, who was revealed to be nothing more than a petty crook and a wuss in his last appearance.
And Alistair Smythe, who Took a Level in Badass by becoming a mutant and leaving the Kingpin's services only to end up becoming a flunky for Silvermane in an even less important position than he was as the Kingpin's lackey.
What An Idiot: In "Day of the Chameleon," none of the SHIELD agents present noticed that "Nick Fury"'s eye-patch was on the wrong eye, despite being right in front of them. Spidey was briefly fooled, too, but he noticed after mere seconds and despite being farther away.
The Woobie: True to the comics, the sheer amount of crap poor Spidey gets put through over the course of this show, particularly from the second season onwards, is unbelievable.
Woolseyism: In the Russian dub, a direct translation of "venom" wouldn't match the lip movements, as well as sounding somewhat awkward. What did they change it to instead? The admittedly cooler name, "Black Death". In later translations his name was translated as "The Death Bringer".
Also in Russian dub, all mentions of "plasma" changed to "blood". Mentions of deaths also were added.