Mainly involving Kari's relationship with Davis, and whether or not she's genuinely Oblivious to Love, aware but uninterested, trying to make him jealous, stringing him along, or just can't decide between him and TK. The Movie (the American version that is) is especially a goldmine for this, since she mentions going to New York with TK to make Davis jealous and notes that she is sure Davis misses her, makes one wonder if she doesn't just like using TK to mess with Davis. However, this interpretation of the Movie is caused exclusively by the dub, since she doesn't mention any intention to make Davis jealous in the original.
Then there is TK; is he in love with Kari or does he just see her as a sister? The dub definitely leans toward the former, while the original is a bit more... ambiguous.
In this, A.R. Pulver gives a bit of analysis into "Angry T.K.", suggesting resentment at being friendzoned by Kari.
The psychology of Ken and the Kaiser/Emperor has been a perennial favorite subject of the franchise. For example, during Ken's stint as the Kaiser, how much of his thought process is Ken and how much is the Dark Seed that was implanted in him?
Davis' infamous crush on Kari becomes much less of an issue over time. Did he actually move on, or did he continue to harbor unstated feelings? (A lot of fanfic angst has been written on the assumption of the latter). It's worth noting that in the movie that takes place after the series, his crush does seem to still be present, although from the perspective of those who followed the English dub (as previously the dub had portrayed him as far more obsessive), it seemed more toned-down.
In the CD Drama Natsu e no Tobira, Daisuke's feeling a little angsty that Hikari turned him down when he asked her for a date.
Sam, Ken's late older brother. How much family angst between the two happened was Sam's fault and how much was Ken's? How greatly was the Dark Spore distorting Ken's perceptions and memories of his brother?
Let's agitate the shippers with the question of whether Sora has feelings for Taichi or not. Original head writer Kakudou explicitly rejects the idea, but the voice actors and other writers on board seemed to favor the ship. The movies certainly generate Taiora Ship Tease, even in Diablomon Strikes Back, where she and Taichi react to one another faster than Yamato (her boyfriend) does (although it should be mentioned that this could be considered a case of Depending on the Writer as Kakudou was not behind those movies). On the flip side, there's the question of whether Taichi has feelings for Sora; in the dub it's made quite clear, but in the Japanese version the only thing that could be potentially interpreted as this is a seemingly wistful look and a comment from Agumon that he's become like an adult (i.e. potentially being interpreted as him having gracefully decided on I Want My Beloved to Be Happy).
Arc Fatigue: The Digimon Kaiser arc takes 21 episodes to actually conclude, because of a huge number of episodes that simply provide Character Focus without moving forward with the plot. It takes three episodes to assemble the Five-Man Band, Matt, Joe, and Mimi each get focus episodes, there's an episode about the TK-Kari-Davis Love Triangle, there's an episode for the Kaiser and Davis, there's a three part mini-arc involving Agumon's enslavement that concludes with Raidramon's appearance, an episode that might have been meant to demonstrate that V-mon could use both armors interchangeably, the episode where the staff got bored with the arc and had Kari get kidnapped by a pack of Eldritch Abominations, two independent Shurimon episodes, a Submarimon episode, and FINALLY a five part mini-arc conclusion.
Ass Pull: The explanation about why the old kids can't use their crests. The last episode of 01 made a big deal about the kid's crests being their HEARTS, and how they could still use them after the amulets were destroyed. Apparently, they went back to the digital world somewhere between 01 and 02 and sacrificed their crests in order to rebuild the world, which came off as incredibly forced shoehorning.
Author's Saving Throw: Digimon Adventure 02 uses a lot of its merchandise to "correct" presumed flaws in the anime's storytelling, primarily regarding a lack of Matt-Sora development. Look at the jacket art for Image Song and other music releases and they'll be in their own little world.
There was a bit of kerfluffle over Miyako ending up a housewife with children in the finale. In the Girls' Festival CD released right during the Tamers era gave Miyako an Image Song about how she wanted to become a Yamato Nadeshiko, and a bit of Japanese merchandise featuring the 02 kids as grown-ups mentions that Miyako is actually only on maternity leave.
Remember Angemon, who was so powerful in the first season that he didn't start making regular appearances until everyone else had reached the Ultimate-level? Well now he exist to get Worfed and DNA Digivolve with Ankylomon, even when they fight against Digimon he should have a clear cut advantage over (the Daemon corps) he doesn't fare any better. MagnaAngemon initially avoids this trope at first. He actually puts up a good fight against BlackWarGreymon when no other Digimon up to that point could scratch him (and it's worth nothing that BlackWarGreymon is not actually an evil Digimon so MagnaAngemon doesn't have a special advantage, MagnaAngemon is just a really powerful Digimon) and only lost because BWG managed to cut off his power source. He then gets hit with this trope when he only appears to give his power to Imperialdramon to help fight SkullSatamon even though SkullSatamon is a Digimon that MagnaAngemon should have had no trouble walking all over.
Magnamon is another example (and a magnificent example of how the franchise's Power Levels are all over the place). When he first appears in The Movie he and his associate Rapidmon can take down a very powerful Mega. Seraphimon and Magnadramon (two legendary and very powerful Mega Digimon in their own right) appeared just so Davis and Willis could have the Golden Digimentals to golden armor digivolve their Digimon. However, when Magnamon appears in the series he struggles to defeat Chimeramon (who was originally meant to be Mega-level, but later material insists on treating him as only an Ultimate). Later sources have been remarkably inconsistent as to Magnamon's general power level — in Hyper Colosseum (the original Digimon Trading Card Game), mechanics required Magnamon and all armors to be treated as Champion-level fighters, while in Digimon Savers, the Magnamon who appears (in his full role as Royal Knight) can go toe-to-toe with Megas. Nowadays the series seems to have compromised by grouping all Golden Armor evolutions with the Ultimate level (which behavior started with the Digimon Story series of games).
Omnimon, who wiped out an army of Diaboromon in his first apperance, can't handle a swarm of Kuramon during his appearance in Diaboromon Strikes Back. Not only is Kuramon Diaboromon's weaker, unevolved form, there were fewer Kuramon than there were Diaboromon, the entire scene makes no sense unless you look at it as the writers fumbling to bring out a brand new form. On the other hand, Omnimon made a beeline for Diablomon and succeeded in the goal of dispatching the main threat... only to belatedly realize how Diablomon's new plan actually revolved around the Kuramon.
Mummymon. In his debut appearance, he managed to hold his own against the new Digi-Destined long enough for him and Arukenimon to escape. Later on, he couldn't take down one of them by himself even when he was at a higher level.
Davis was and still is one of the most polarizing members of the new cast. Being a Suspiciously Similar Substitute to Tai and turning the previously unchallenged Takari ship into a Love Triangle (in which he's the underdog) managed to earn him a boatload of attention, positive and negative alike.
Sora's Girliness Upgrade, either you see it as a sign of maturity and acceptance with her mother or you dislike it as she becomes flanderized into a generic girly girl and loses her unique Tomboy personality.
Even the villains aren't safe; depending on who you ask, Arukenimon and Mummymon are either a pair of hilarious sympathetic villains, or they're two of the most annoying, useless villains this side of Team Rocket.
Blackwargreymon is either a badass and a compelling tragic antagonist, or an overly emo Mewtwo knock-off whose presence wore out its welcome and who needed to dial back on the Wangst.
Expanding Digimon family trees getting Ret-Conned into the Adventure-02 universe.
Angewomon, whose classic Mega form is Holydramon (seen in Hurricane Touchdown and Digimon Rumble Arena), evolves into Ophanimon in Digimon Battle Spirit 1.5 and in the Digimon Adventure PSP game. Fans are split as to whether this change makes Gatomon's evo-line boring, or even how consistent it is. The Ophanimon fans refer to the fact that she and Angewomon are both Angel digimon, while the Holydramon fans mention how the Holy Dragon is coming full-circle (Salamon and Gatomon are both Holy Beast Digimon), and that traditionally, high-ranking angels (Seraphs, Ophans and Cherubs) were strange-looking to human eyes, making it counter-intuitive to exclude Holydramon on that basis.note It should be noted that the video games are Bandai products, not Toei, so despite the fact they're technically official products their canonicity is suspect.
Davis ends up getting a few big moments almost all to himself later in the series. Most notably, Davis is the only user of the Digimental of Miracles (his fans are happy to assign it to him) and is immune to MaloMyotismon's Lotus-Eater Machine due to being mostly content with his life and having his priorities in ordernote He also technically "helps" the other Digidestined escape from their illusions, but the Digimon partners have already helped them banish the illusions by the time he and Veemon's armors come to collect them. His detractors especially resent this last part, feeling it's unfair that he isn't terrified into submission like the others after witnessing the monster's cruelty.
V-Mon as well, being the primary Digimon partner. He has more armors than the rest, including a Golden Super Mode, for example.
If you didn't ship Yolei with Ken, you were expected to hate her. Even worse when she did get him.
In their heyday, the Dakari vs Takari fights were the worst. Generally in fanfics, the character the author didn't prefer would get Ron the Death Eater Treatment.
Back in the early 2000s, Sora won the award for being possibly the biggest Scrappy of all the characters when she and Matt hooked up, as the biggest shipping factions at the time (Tai/Matt, Tai/Sora, and Matt/Mimi) basically ganged up on her.
Matt himself got this treatment from angered Tai/Sora fans.
Draco in Leather Pants: Interestingly averted with the Digimon Kaiser/Emperor. Fans still loved him, but never tried to justify what he did and were happy to see him turn good, but only after he'd paid for what he'd done. His terrifying vision during the final battle probably helped gain Ken some serious sympathy. It also helped that the fans didn't have to invoke this trope as the show created a perfectly reasonable backstory for why he became this way.
Natsu ("Nat-chan") from the CD drama Natsu e no Tobia (Door to Summer) has become very popular within the fandom, even more then half of the main cast, and that might be perhaps because of The Woobie status she has as well the interactions she has with Daisuke, who becomes more of a fleshed out and sympathetic character in the CD drama.
Jun Motomiya as well.
Epileptic Trees: In the penultimate episode, MaloMyotismon traps the DigiDestined inside a Lotus-Eater Machine which lets them see their greatest desire, but Davis breaks the group out as his greatest desire is to defeat MaloMyotismon once & for all. A common theory amongst those who absolutely hate the events following this is that Davis doesn't break the group free of the illusions, and he's merely seeing his greatest desire & MaloMyotismon has really won, unbeknownst to the viewer.
Evil Is Cool: The Digimon Kaiser, to the point some fans actually prefer him over regular Ken. Black War Greymon as well, for those who didn't find him overly emo.
Davis' problem early in the season was that he was hesitant to take action — for example, not wanting to attack Agumon, who had been kidnapped and brainwashed by the Digimon Emperor, despite there being no other way to remove the Dark Spiral. There's also the episode where Ken "kidnaps" all of Davis's friends and then forces Davis to pick between them. Davis is completely unable to react in this situation, and is on the verge of offering himself in their place. Ken is untrustworthy.
Another possible example is when Cody refuses to take the digiegg of Reliability since he told a lie, and Joe give him an inspiring speech about how, while some lies are hurtful, there are some lies which are not only acceptable, but helpful. This one pulled him out of a possibly important exam because Cody was telling him that his dad was in the hospital. Even if it was a life and death matter, there was little thought put into keeping up The Masquerade.
After a season of breaking the Digimon Emperor's Control Rings and destroying fake Digimon created from Control Spires, Cody and Yolei have to learn that sometimes, the only way to stop a bad Digimon is to kill it. In the first season, this was never really questioned, probably because it happened more often and their survival depended on it— the first season team was trapped in the Digital World, while Cody and Yolei were able to go home every night.
Fandom Rivalry: With Tamers fans. 02 fans consider Tamers to be unfun and wangsty and wish it was a continuation, Tamers fans consider 02 to be insultingly childish and consider it being the end of its continuity to be just desserts.
Fanon: If you'd listen to the fans talk, you'd believe Dagomon is a Physical GodEldritch Abomination that could give Apocalymon and Armaggemon a run for their money; there's a certain desire to ignore that ol' Squidface is just an Ultimate/Perfect level Digimon.
Fans were not happy with the explanation given for why the old Digimon could no longer reach Ultimate for multiple reasons, especially since it was just a blatant example of the show nerfing the older kids to allow the newer kids to stay relevant. Especially since it only theoretically works if you ignore the Digimon Wonderswan Series.
Gennai's commentary on Gatomon's tail ring at the end of the series is an equally blatant excuse for completely forgetting and failing to incorporate it back into the series after she lost it in the first episode.
Fan Preferred Pairing: While Sora/Yamato is canon (and personally favored by the original director of Digimon Adventure), many fans still prefer Taichi/Sora, and you'll be more likely to find fanwork and doujinshi for that pairing. Even a few of the Japanese voice actors have stated their preference for Taichi/Sora and expressed surprised that Sora ended up with Yamato instead.
Throughout Episode 23, Ken reflects how he's lost his heart and needs to find it. Years later, his voice actor would go on to play another guy who lost his heart.
Imperial Dramon's "Positron Laser" attack. In 2008, scientists actually discover a way to produce antimatter (namely positrons) in large quantities by using a laser.
Ho Yay: Oh so much. It helps that the whole DNA Digivolution aspect provides a handful of same-sex pairs to work with. (Ironically, it's suspected that this was originally intended to prevent Does This Remind You of Anything? regarding the merging of entities and simultaneous heartbeats with an opposite-sex couple.)
Informed Wrongness: While you can rightfully accuse Davis of rash judgment when the team first discovers Control Spires in "Iron Vegiemon" with his guns-blazing approach, the solution the group instead hits upon is an odd example of Informed Rightness when Matt decides to go with equally rash tactics that rely entirely on The Guards Must Be Crazy. The show takes Matt's side and none of the guards take notice of the fake Dark Rings (which even Patamon thinks is dumb) until the prisoners launch an uprising.
Iron Woobie: Ken, for his persistence in knocking down Dark Towers, even while fully expecting the rest of the team to continue hating him, and his concern for the Dark Seed kids, who followed Oikawa of their own volition.
Memetic Mutation: "Original Digimon do not steal", after some fans noticed that Kaiser-Ken's creation of what he insisted was his "original Digimon" was similar to behavior of many people on DeviantArt.
Mind Game Ship: The Emperor's iconic Sadistic Choice — which one of Davis' friends will he save from being eaten? This scene is basically responsible for the entire Kaiser-Daisuke fandom.
Ken: Seeing you squirm is so delicious.
Misblamed: Dagomon is widely regarded by the fandom as being responsible for Kari's kidnapping to the Dark Ocean, but it was actually the Deep Ones that summoned her and tried to mate with her.
Ken's literal Kick the Dog moment, which suffers from a laughable sense of physics.
The Big Bad's dub name. "Malo" is the Spanish word for bad. The Big Bad's final form is "BadMyotismon".
Due to Never Say "Die" being in effect, hearing the characters constantly go on about "destroying" evil Digimon was quite narmy.
Nightmare Retardant: Wendigomon's flavor text serves to Double-Subvert this; basically, the spaciotemporal mindscrew is Wendigomon's own powers. It was, however, the virus that made it an Eldritch Abomination.
OT3: After the shipping wars cooled down (which took at least half a decade), there sprung up a few sub-genres exploring the Triang Relations between Taichi, Sora, and Yamato on the one hand and Takeru, Hikari, and Daisuke on the other.
Pandering to the Base: Blackwargreymon's fight against Wargreymon. It is as awesome as it is unnecessary. It really doesn't make sense for Azulongmon to give Agumon the power to become Wargreymon just to fight BlackWargreymon, but the fans wouldn't have been satisfied if we didn't see the two Wargreymon go at it.
A rather famous example with the Adventure "Love Triangle", a combination of this trope and Depending on the Writer. Hiroyuki Kakudou always intended for Taichi and Sora to be Just Friends, and for Sora to fall in love with Yamato as a way of subverting the cliché that main boy and girl had to end up with each other, so there was never any Love Triangle originally. This was also the plan for 02 until Our War Game! complicated things. Basically, Mamoru Hosoda was unaware of the intended Official Couple and made a fight hinging on Belligerent Sexual Tension a major plot point in the Our War Game! movie. When Sora began dating Yamato in 02, many people were confused at the sudden change in love interest, even the voice actors. In the English dub, the Relationship Upgrade between Sora and Yamato looked totally random and Strangled by the Red String.
Davis freakin Motomiya. Back in the day when the Ship Wars were in full swing, you couldn't turn around without seeing some Takari fanfic where he was written either as a jealous psychopath or so braindead it's a wonder he could tie his shoes, never mind be a Digi-Destined.
On the other hand, there's an entire genre of fics where the other Digidestined (most frequently Yolei, TK, and Kari) are derailed into jerks who talk badly about Davis behind his back, thus giving him a reason to leave the group.
The Scrappy: While, as mentioned above, this season does have its share of base breakers, you won't find many people who'll defend Shakkoumon. They mainly cite his strange designnote He's based off of a Dogu statue as their reason for not liking him, often calling him a "teapot", among other things.
Seasonal Rot: Apart from the controversy surrounding the Distant Finale, the series seemed to change plots as often as someone changes clothes. This is especially poignant in the small (yet important) Holy Stones arc. These world-shattering sacred rocks were never mentioned until Mummymon casually talked about it in a 10-second conversation. There was little foreshadowing, and once they were all eliminated, they never came up again. Additionally, most revelations about The Man Behind the Man seemed to come out of nowhere, and Chiaki Konaka's Cthulhutastic guest-writing episode - originally intended to set up another subplot - went completely unexplained, was almost never referred to again (except in the episode featuring the Daemon Corps, which Konaka also wrote), and comes off as a Big Lipped Alligator Moment. It generally reeks of a series where they had plenty of ideas, but perhaps had too many and were very careless and haphazard about how they applied them.
Sequelitis: The general consensus is that as a sequel to Digimon Adventure, this didn't work out as well, which may be why the Adventure continuity was scrapped in favor of new ones each series afterwards.
Shipping: With two significant Love Triangles and Ho Yay beyond that, it runs rampant in the fandom. Just check this page. We could run an entire page based on the couples and issues that went through in the making.
Squick: In the original version, the King of the Dark Ocean's minions weren't trying to get Kari to destroy their Evil Overlord. They were trying to bring Kari to them so that they could mate with her. She reacts more or less exactly like you would.
Strawman Has a Point: Davis tries to convince the team that Ken has changed and have him on the team. While the other kids (especially TK) do feel that he has changed, they felt that it was too soon to trust the person that they have been fighting for months on end. It would've been a better-made point if he hadn't spent so much time talking about the Crest of Kindness, though.
Mayumi Yamaguchi (Gabumon): Honestly, Sora! If youíd spent just a few minutes to ask [Gabumon] for advice, I would have said, ďSora, donít do this to yourself. Itís Taichi you should go for."
Yuuto Kazama (Yamato): Itís tough work taking care of Yamato, youíre saying?
As to whether the Love Triangle actually exists, the scene important to it in 02 makes the idea of whether Taichi has feelings for Sora incredibly vague. The PSP Adventure game (which, as a Bandai rather than Toei product, is a product of questionable canonicity and potentially moreDepending on the Writer) gives an alarming batch of mixed signals from all three parties on top of this.
In the expanded universe, there are eleven Armor Digimentals for the Digidestined to use (out of a technical total of fifteen), making for over sixty armor-digivolutions accessiblenote Each of the main six "ancient species" Digimon — V-mon, Hawkmon, Armadimon, Patamon, Tailmon, and Wormmon — can use the Digimentals of Courage, Friendship, Love, Purity/Sincerity, Knowledge, Faith/Reliability, Hope, Light, Kindness, and Miracles to evolve into a unique Armor Digimon, while V-mon and Terriermon can also use the Digimental of Fate to evolve. Michi e no Armor Shinka established that the children could, in fact, swap Digimentals (when they do so on accident), and the unique forms can be used in the D-3 handheld toy that was released at the time. In the actual series, the Chosen only ever use their specific -mentals, highly likely to slim down the amount of ensuing Transformation Sequences. (Digimon Tamers takes advantage of the extra fifty-something Digimon by having them bio-emerge — that Lynxmon Rika fights in the first episode? Give Tailmon the Digimental of Courage).
Only a minor fraction of the available Jogress/Armors were usednote Outside of Kari's Imagine Spot, the only "canon" Jogress we never saw was DinoBeemon.
Ryo, of Wonderswan and Digimon Tamers fame, technically has three (3) games in between Digimon Adventure and Adventure 02, one of which involves Ken and two of which have him partnered with V-mon, but none of which have any serious lasting impact on the world of 02note With apologies to the Digimon Kaiser, who is, frankly, incidental to the impact Milleniummon should've had. For some more specific ideas, how does V-mon feel about Daisuke being his second partner after two campaigns with Ryo, and vice-versa? What are Wormmon's thoughts on the scenario (only Ken has amnesia, after all)? And even if we know about V-mon and Wormmon, how about Hawkmon and Armadimon? They were sealed in Digimentals like V-mon was; do they have any history with him?note In Tag Tamers, Ryo receives eggs that hatch and grow into Hawkmon and Armadimon, respectively. Are these the same Digimon?note In Brave Tamer, Hawkmon comments that Ryo feels vaguely familiar, though he's not sure why. Of course, considering the array of different Timey-Wimey Balls that were ongoing over the course of that game on- and off-screen, this doesn't necessarily mean anything by itself.
Tough Act to Follow: In a shuffling and reshuffling of Deader Than Disco and Vindicated by History, generally speaking deep critical analysis of Digimon by the involved fanbase has fallen into a consensus that it isn't the worst Digimon anime series, but had the misfortune of following Digimon Adventure, a series that was comparatively thematically coherent and had far more developed characters.
Vindicated by History: It's either this or Deader Than Disco. Quite simply, the fanbase absolutely cannot decide how it feels about this series. Near the time it initially aired, it was extremely popular and was considered by some to be an Even Better Sequel to the original, but outcry over the Distant Finale, the fact it was followed by the generally well-received Digimon Tamers, and general retrospective analysis of its writing quality caused general opinion of it to plummet. Then, in the wake of some of the later series (particularly Digimon Xros Wars: The Young Hunters Leaping Through Time, the protagonist of which ended up being often compared to Daisuke), some opinion of it improved to a perception that it wasn't the worst Digimon series out there. Due to the series' divisive status, whether it's been Vindicated by History or Deader Than Disco (or neither) depends entirely on the person you ask and their own personal opinion on the series.
The Woobie: Ken, of course, Wormmon, and Wallace from the movie (whose story makes Davis cry).
Pipimon, Oikawa's partner Digimon. It waited many years for Oikawa to show up, only for Oikawa to die in front of him after they just met.