In the very first Digimon Adventure the Monster of the Week for the first few episodes - Kuwagamon, Shellmon and Seadramon - aren't tainted by any sort of evil magic or science, and don't speak, which is very unlike most antagonist Digimon from the rest of the show.
This was particularly a problem for the English dub, which was being produced at almost the same time as the original, which led to mentions in the early episodes of Mimi's non-existent brother, Tai and Kari's non-existent puppy, and Matt and T.K. being half-brothers despite having the same mother and father.
In the very first episode, Tai and Izzy are taken to a 'hiding tree' by their Digimon to hide from Kuwagamon. These are never seen or mentioned again.
Digimon In general. In the earliest adaptations, including first ever appearance in C'mon Digimon, human partners could not make their monsters evolve at will, evolutionary levels were a lot less important over all, quite a few Digimon characters actually had names and monsters rarely called attacks. And monster was the preferred short hand human characters used for Digital Monsters rather than Digimon. The art style has shifted too, though that is not as noticeable since designs have rarely been upgraded after C-mon.
YuYu Hakusho had early chapters (as well as early episodes) involve him solving cases involving demons from the Spirit World (the manga even more so as a good chunk of the early chapters were nothing but Yuusuke floating around the afterlife trying to do some good deeds; in the making of the anime, they even skipped whole volumes of this. Impressive, considering the near lack of filler). By the time the Toguro brothers were introduced, it became more focused on his combat abilities and strengths fighting demons rather than solving cases.
The very first scene of Tengen Toppa Gurren Lagann is clearly supposed to be foreshadowing a scene from later in the series... Except, that scene never ends up happening. Even to a long-time viewer of the show, it makes very little sense and doesn't gel that well with how the story lays out. It's clear that at this point, only a loose version of the complete story was ready.
Fans were eventually handed an explanation when one fan asked if it was an alternate continuity where the Spiral Nemisis happened. The response? "Sure, let's go with that."
The first few volumes (and episodes) of Bleach were primarily a Monster of the Week storyline. Then the Soul Reapers got introduced, and the plot shifted gears, eventually leading to an all out war.
Mahou Sensei Negima! was originally a Harem Series... for all of two volumes. After that, more and more shounen elements were added, to the point that other than having some of the same characters, some of the most recent chapters look like they're from a completely different series. Pretty much everything from volume 10 or so onward is a straight action manga with comedic and harem elements. If you compare Negi's early flaws (timid, gets scared and runs away) with his later ones (aggressive, too solitary) the contrast is very sharp and can't entirely be chalked up to character development.
This was actually done intentionally by the author, interestingly enough, as 'the shift that occurs roughly during the third or fourth volume was a sneaky method of getting past some Executive Meddling: Ken Akamatsu wanted to do a straight-up Shōnen fighting series, whereas his editors wanted him to do another Harem comedy due to the success of his previous manga, Love Hina. The shift at first is subtle enough to work.
The first season of Magical Girl Lyrical Nanoha, particularly its first episodes. Even ignoring the constant Genre Shift of the franchise, there are several elements that are out of place now that the series has several rules set. For example, Devices apparently needed a long incantation to unlock (Nanoha being able to do it with a simple "Please" was shown to be special) and they were apparently shapeshifting weapons that could become whatever its owner imagined them to be. These two features were quietly discarded after the first three episodes and never mentioned again.
Heck, Yuuno's mere existence is one, being a mage who isn't a familiar that became a ferret when his Mana was low, a trait unique to him in the setting after four/five seasons. The latest explanation at the start of Sequence 1-1 (i.e. Chapter 5) of The MovieManga was that the Earth's magical field was incompatible with him, turning him into a ferret after he ran out of energy. Another of Yuuno's unique abilities, Temporal Force Field, turns out so ridiculously overpowered by the time the series' magic rules are formalized that it is never even brought up again from season three onwards, where the heroes instead have to organize mass evacuations when they have to fight in urban environments.
The series title is a leftover of this trope. Early on, an episode revealed that "Lyrical" was suposed to be Nanoha's special magic word that gave her more power. It's never mentioned again. Ever.
For its first story arc, Dragon Ball was an updated retelling of Journey to the West with a few vague science-fiction elements. When it came to the Tenkaichi Budoukai story arc immediately thereafter, it jumped feet-first into martial arts action, and when the Red Ribbon Army was introduced immediately after THAT, the world became openly, and proudly, Fantasy Kitchen Sink for the rest of the series's run.
If one considers the entirety of the continuum, Dragon Ball acts as a series long Weirdness to Dragon Ball Z. The moment Raditz showed up and opened Earth to the greater galaxy beyond was the point when the theme and story shifted heavily. It's no wonder the anime made them separate series.
One element early on in the series that really sees some head-scratching is the conclusion of the Boss Rabbit storyline. Considering it ends with Goku actually going into outer space with no space suit and dropping the villains of it off onto the moon, it always feels weird seeing climax of the Frieza Saga where Goku has to escape the dying Namek in time, since if the explosion doesn't kill him then the vacuum of outer space will. And Piccolo blows up the moon later on, presumably with the Boss Rabbit still on it.
In the first five or so volumes of Oh My Goddess!, Keiichi wasn't as shy around women (though he was still squeamish), seemed like more of a plain Unlucky Everydude than a mistreated Nice Guy, and Belldandy seemed to know more about Earth than her anime adaptations, was quick-witted, and dressed in an elaborate Oriental-style robe. The series began as basically a college-student drama with a goddess in it (later two, when Urd showed up, and three, when Skuld appeared). After the Lord of Terror Arc, and began to resemble more of a cross between a Dom Com and a Fantastic Comedy.
Belldandy didn't just seem to know more about Earth, there were various implications that she was a bit of a Bitch in Sheep's Clothing and was subtly tormenting Keiichi in revenge for his getting her stuck on Earth. This was obviously dropped in favor of her being Incorruptible Pure Pureness incarnate (to the point that shackling a demon to her turned the demon into an angel). Urd was also much more heavily implied to be an Anything That Moves vamp at the start, which settled down into her being just sensual. About the only one whose characterization isn't hit with this is Skuld, who showed up after the series began to really gel.
The first series of the anime was rather different from all subsequent series, with Usagi using several attacks and items that were scarcely or, in some cases, never used again after their debut appearances. The Disguise Pen was used very frequently, but quickly fell into disuse early on in the R series. The overall tone was also quite different—the enemies faced by the Senshi were much more menacing and threatening. Contrast with later seasons, in which the Quirky Miniboss Squads become hilariously incompetent and the Monsters of the Week are often complete jokes who rarely pose any serious threat. It's no wonder fans generally prefer the earlier seasons and tend to ignore or even disown the later ones.
The first episode has the Monster of the Week operating by replacing an actual person (Naru's mom) in order to infiltrate the human world. For whatever reason, this M.O. was rarely used by the subsequent youma Beryl sent.
In the manga, Usagi started out with a pair of goggles resembling what Sailor V wore. She would discard them after the first few appearances and after she gets her first Mid-Season Upgrade, is never seen again with them. Both the original anime and Sailor Moon Crystal flat out never used them (which is particularly odd with Crystal as it's supposed to be more in line with the manga.)
Yami Yugi's appearance came off extremely sinister in early chapters of the manga. Gradually his appearance shifted so that he just looks like a more confident version of Yugi by the end of the first volume. The first couple of chapters, however, he looked downright psychotic. He also regularly made people go insane in punishment games and even (most infamously) set a man on fire.
In his first appearance in both anime and manga, Kaiba is initially portrayed as an antagonist. Later on, while still being a Jerkass, he's never (at least not intentionally) working for the bad guys.
The English Dub is infamous for cutting out all references to or hints of death or violence, but surprisingly was a bit more lenient on it in the earlier episodes, especially during Yami Yugi's duel with Panik where Panik attempting to light Yugi on fire if Yugi loses, amazingly enough, is left intact.
Even the cards are this. In this series they are mostly inclined towards the horror genre, religion and mythology note especially but not restricted to Ancient Egypt which doesn't help their uncanny designs. Later series since GX have a "futuristic and dragons theme" for the cards and never looked back since. While nightmare-inducing cards still exist, it is not as frequent or as extreme as in the early days.
Even when the series becomes about card games, the first season, Duelist Kingdom, was completely full of notoriously bizarre interpretations of the actual rules of the Yu-Gi-Oh trading card game. Very frequently, the anime duels would sharply deviate from how the cards actually worked, to include one memorable instancenote the "Catapult Turtle gambit" in Yugi's duel against Panik that was once the Trope Namer for Screw the Rules, I Have Plot!, and without a whole lot of continuity in how they were applied. This is partially because the actual card game itself was going through the height of its own Early Installment Weirdness. Once the action shifts to Battle City, the anime does a better job of following the rules of the card game, with a few exceptions.
Given that the principal heroes of the third, fourth and fifth stories are Jotaro Kujo (Japanese), Josuke Higashikata (Japanese), and Giorno Giovanna (originally Haruno Shiobana, half-Japanese), it may surprise new readers that it took a very long time to get to Japan. In the first story, the main hero, main villain, and their families are British, as are pretty much all the enemies, and the hero's mentor is Italian. The second story revolves around an either naturalized or expatriated American (who's the son of an RAF pilot) who teams up with a descendent of the Italian mentor from the first story and eventually tangles with a band of Nazis. Aside from one or two cameos, there isn't a single Asian of any stripe in the first two stories.
The Land of Waves Arc has much more realistic and 'gritty' feel than the main plot, the Non-Action Big Bad being a sharp suited shipping magnate trying to prevent a bridge being built to an island village so he can continue exploiting its inhabitants and the ninjas being mercenaries doing a job - in fact, it is the only storyline focusing on the ninjas' role as assassins. The technology base also seems to be closer to our world - there is a caterpillar-tracked crane shown in the building scenes, and one panel even shows a gun behind a shop counter.
An overlooked example from the same arc is that Sasuke seems unaware of who killed his clan. He at one point suspects Kakashi due to the latter's Sharingan, but that obviously wasn't true.
Might Guy summons Ningame, a ninja turtle, in his first appearance. This is odd because Guy would pretty quickly establish he fights purely with taijutsu, and nothing else outside the databooks would indicate he was even capable of either ninjutsu or genjutsu. Ningame does get summoned once again years later in a rather funny scene that lampshades the whole bit.
Guy specializes in taijutsu, but is capable of the other two. The reason we never see him do otherwise is because he continues to only use taijutsu to inspire Lee, who is quite literally incapable of performing the other types.
The first English dubbed episode of InuYasha involved a fair amount of Ye Olde Butcherede Englishe from villagers and Kaede. By the following episode, it was entirely absent aside from Kaede's "ye". Considering how horribly forced one villager's reading of a particularly convoluted line was, this was a blessing.
Most of the weirdness in Slayers is two-fold: It began as a self-aware parody of fantasy series, albeit with its own dogma. As soon as the story began to emerge some time in the middle, the self-awareness angle was dropped. Also, earlier, the characters were far more cooperative with one another, and whatever new magic showed up garnered an explanation for the viewers. Newer seasons had a lot more friction (to the point that Zelgadis would continually try to run away) and dropped explanations.
In the first anime season, the four Filler episodes that were meant for comedy actually are a part of the plot - and mixed in a way that was done very well (all four episodes involve a humorous incident occurring during what is basically a bounty hunter chasing the protagonists). The second season fillers were only marginally related to the plot, and then by the third, they became more like the standard trope.
This happens in the novels as well; the first story arc is one long narrative, the second is more episodic.
Early in the manga version of Urusei Yatsura, Ataru was the only main character, rather than sharing that status with Lum (chapter 2 didn't feature Lum at all)note Originally, Takahashi had conceived of the series as an anthology series, with Ataru running into a different group of "obnoxious aliens" each installment. It was only that Lum became instantly popular that Takahashi did an immediate retool of the concept. In the game of tag in the first chapter, Lum isn't shown to have her electrical-shock ability, unlike in the anime adaptation. There were also many examples of Art Evolution (Cherry was drawn taller than usual, male characters had Big Ol' Eyebrows, eyes were drawn more realistically and less tall-and-narrow, etc.) Lum was also much more ambiguously antagonistic and perhaps even malevolent at the beginning, as opposed to the sweet naif that she became later on. For instance, in an early installment, Lum continually lies that she is pregnant by Ataru, both to wind up Rei (a shapechanging member of her race who was once engaged to Lum and is intensely jealous) and to twist the dagger in Shinobu... and Lum is clearly deriving pleasure from the chaos she is sowing. The Lum from even a year later would not do things like this.
The "Ataru is supposed to be the only main character" and Lum's growing role were later lampshaded in a later storyline: when Ataru tried to resign from the post of class president and give it to Mendo, everyone assumed he was resigning from being the main character, with Lum being the exception because she was convinced the main character was herself.
Shinobu was less hot-tempered in early installments and didn't yet have her super-strength. One chapter showing a possible future even hints at her and Ataru getting married and having a child together. As the anime took more cues from the retooled plot and increased focus on Lum and Ataru as a pairing, this chapter was one of the stories that were skipped over.
Mendo was not Ataru's rival in the first volume, but instead his role was taken by four (sometimes five) nameless classmates who would wind up dragged into the strange adventures. Oddly, while Takahashi phased these characters out in favor of Mendo, the anime gave them more roles.
When the Death Note manga first introduced L, he actually stood up straight, but he was then given his slouch when he revealed himself to the Kira Task Force.
L was also depicted with eyebrows after revealing himself, but they quickly disappeared over the course of the manga. Pre-revelation, his hair was more on the curly side of messy and longer, instead of his memorable spiked style.
In a case of Art Evolution, Matsuda looked closer to Raye Penber when first introduced. Mogi's face was also more on the cartoonish side, with his eyes being much wider and bulging. Matsuda was also more serious when he was introduced. Characterization Marches On when he became more of a Plucky Comic Relief after L revealed himself to the KTF.
In the early manga, Light was shown to have two friends from school. The anime adaptation excluded the characters to depict him as more of a loner.
While Mello is memorable for his black outfit and baring his midriff, his initial manga appearance depicted him with white pants and his vest covered his abdomen.
The very first color image to feature Mello and Near (pre-timeskip) had both boys depicted with pure white hair. This was due to Ohba and Obata still struggling with ideas for the two at the time, with one idea for them to be twins (or at least resemble a pair). After their personalities and designs were finalized, Mello's hair became blond in all later color images.
The first couple of chapters of Mysterious Girlfriend X are way more direct about sex than the rest of the series. Among other things, Tsubaki actually dreams about having sex with Urabe. Later in the series, dreaming of mere contact is enough to blow his mind.
The first chapter of the first season of Rosario + Vampire has this effect. Saizo Komiya hulks out into a massive, veiny, humanoid... thing with a snake tongue, and neither he nor Moka gets an entry in the Bite-Sized Monster Encyclopedia that everything else does. In addition, Inner Moka isn't nearly as harsh as the rest of the series, almost flirting with Tsukune. The encyclopedia problem is remedied later on; the bonus chapter to conclude that season provided an Encyclopedia entry for vampires, and it can be assumed that Saizo is a monstrel like the rest of the Anti-Schoolers.
Since the movies are made at the same time the new series is being done, it's easy to spot out how different one character acts in one of the Pretty Cure All Stars movies than they do in-series. For example, Erika is easily shown diving into Tsubomi-level doubts and worries in DX 2 where she's shown in the series to be in almost constant Genki Girl energy levels. And after watching the All-Stars movies, watch either Futari wa Pretty Cure or Yes! Pretty Cure 5. Futari wa was a parody series that really took off while Yes! was a lot more girlier (compare Yes! version Cure Lemonade to GO!GO! version Cure Lemonade, for example).
The first OVA series was much more attached to its harem roots and was easily more sexualized and "mature" (Noboyuki was The Peeping Tom, Katsuhito was shown groping Ryoko's breasts in one early episode, Washu flipping off Kagato, Ryoko and Ayeka's attempts to win Tenchi flat out) and a few characters' personalities were vastly different (Sasami was shown to be a mischievous Bratty Half-Pint, Ayeka was shown to be a little more haughty and antagonistic towards others, Mihoshi was surprisingly competent especially compared than she is now).
This can also be seen in the manga based on the OVA — the OVA rarely had the group leaving the house except for trouble, where the manga had them going all over the place, especially in the later comics where Sasami's seen going to school.
The English dub also took a couple episodes to find its footing, and originally referred to Ryo-Ohki as a male before correctly switching to female. A couple actors also changed how they voiced their characters (notably Nobuyuki sounds more higher-pitched and nasal in his first episode before Jay Hopper switched to a lower doofus-sounding voice).
Black Butler starts out in some sort of alternate world that's a very close, but not complete, copy of Victorian England, complete with video games, modern suits and television somewhere around 1888. This quickly changes to simply taking place in Victorian England.
In the earlier stories Golgo 13 was much more chattier, even cracking some jokes in comparison to his later characterization as The Stoic.
The first episode of Princess Tutu has a few oddities. There's some weird shadowy animation the likes of which is never seen again in the series (although it is awfully similar to the animation in the promo), and it also includes the only instance of Calling Your Attacks.
The manga was strange in that it wasn't as outlandish as it would be in the future. While yes, the villains in the Grand Line are far more realistic and dangerous than the cartoony ones of East Blue, the way the Grand Line absolutely destroys the laws of physics is nothing short of astounding, making East Blue rather tame in comparison.
In particular is Buggy, who was treated as a legitimate threat in his first appearance (even being a Bad Boss to his crew), but gradually became goofier as the series progressed.
One Piece, in its earlier days, was also known among those who read it to be noticeably devoid of the Male Gaze compared to its brethren in Weekly Shonen Jump. Then, the author fell in love and got married, and now beautiful women are everywhere and has since become a distinctive part of the series.
The original manga may be odd to read, as rather than starting things off with Joe's arrival to the team, the manga quickly goes through the origins of the other cyborgs first. Albert/004, while still a dark-natured character, is also rather louder and hammier early on, and spends as much time smirking as he does with laying on the snark.
The team members (save for 003 and 009) are also given nicknames early on, which aren't referred back to: 001 is "The Brain", 002 is "The Jet", 004 is "The God of Death"/"The Reaper" (both valid translations of "shinigami"), 005 is "The Iron Man", 006 is "The Mole", 007 is "The Chameleon", and 008 is "The Merman".
On at least two different occasions in the early manga, 004 was shown to be able to fire off his fingers like darts/missiles. This did not come up again in the later stories. 004 also originally used his knee missile by rolling up a pant leg and pushing a button on his knee to split his leg in two, while later appearances had him able to automatically split his leg to fire the missile.
007 originally had to manually take off his clothing to be able to pull off a convincing transformation (such as transforming into a dolphin).
002 had a much milder, easy-going personality compared to the brash and louder attitude viewers would associate with him from modern incarnations. However, he did become a bit more hot-tempered and negative in the later stories in the manga, with it being a plot point that at least 20 years had passed since their original adventures and that he was feeling the strain of being a cyborg.
Dr. Gilmore had his eyes shadowed out early on, to mark him as a shady character. 005's pupils also tended to appear and vanish in the early arcs, and 006's height and weight weren't as consistent (with him sometimes not appearing as plump as he would in most media, and sometimes not appearing as drastically short).
The earliest colored artwork for the series depicted the 00 cyborgs as wearing green uniforms (as opposed to red), and Joe/009 had blue eyes in some of the early covers. Other color schemes were also not settled early on; 004 sometimes appeared with strawberry blond hair (as opposed to silver), 003 alternated between being a blonde or brunette, and 001 sometimes had blond or brown hair as well.
003 had longer hair in her very first appearance in the "Birth" arc, and Ishinomori wasn't as consistent on whether or not she wore a headband. Her hair style was altered over the course of the manga, and she was consistently depicted as wearing a headband.
004 had a pointier face, bowl-cut hair, and a pointy nose (sometimes almost rivaling 002's). His facial features and hair cut gradually changed, to where he had a more chiseled face and aquiline nose, as well as less of a bowl cut.
At one point in the early serialization, Joe's surname was "Muramatsu" instead of "Shimamura". This was corrected in tankoban releases of the manga. 003 was also called "Francois" (a masculine spelling) instead of "Francoise", which was also corrected.
In the first volume of Keroro Gunsou, Keroro's Verbal Tic was "ribbit" instead of "Gero". Also, Fuyuki and Natsumi referred to Aki as "mama" instead of "mom". Keroro and Tamama also looked fatter.
Ranma in any least the first chapter/episode while a bit short-tempered was considerably more polite than the Jerk with a Heart of Gold fans know him as. His teasing of Akane seemed to come more from his lack of social skills, and any dickishness. Kasumi was a lot more mischievous than the virtual saint of the series - not to mention her flash of anger calling Genma out on training Ranma in a dangerous area. Nabiki while focused on money, didn't quite have a Money Fetish and was more interested in boys.
Area 88: The first few issues of the manga fell victim to this.
In the first issue, Mickey is much more boisterous and older-looking than in later issues.
McCoy is indifferent to the mercenary pilots' safety in early issues (such as when he sold defective Sidewinders to Boris), but shows warmth and concern for them as the series progresses.
When Hoover is first introduced in the Wolf Pack storyline, he is just as greedy and amoral as the other mercenaries (such as when he was among pilots trying to get free fuel and maintenance from Saki), in sharp contrast to his maturity later on.
Greg is an idiot ball holder in the incident with Gold's documents, but is depicted as competent and insightful later in the manga.
Azumanga Daioh was actually quite tame in the beginning, especially Osaka, who absolutely hated the nickname and pretty much played up the Osakan stereotype just to get people to shut up. As well, Chiyo-chan was drawn just a little more realistically with her pigtails.
Rurouni Kenshin: In the chapter after Sanosuke is introduced, Kenshin is shown to have the ability to sense people's chi, and chi is later used to explain Udo Jin-e's paralysis power. After that Chi, and the ability to read it, is never mentioned again.
A lot of Wandering Sons changes have to do with Character Development - such as why Maho and Saori Took A Level In Jerk Ass or how sensitive Nitori originally was - but some stand as examples. Nitori's baking abilities don't pop up after elementary and the series took a noticeable dive in terms of how fluffy it was around the same time. Takatsuki and Kanako were not childhood friends in the first volume which causes their interactions to differ, and Kanako wasn't The Cutie so she acts uncharacteristic. There were a few kids who hanged around the gang in early chapters but Kanako was the only one who stayed.
Although Kill la Kill often has some level of violence, the show generally has a very low body count because people are either dispatched in vague, non-graphic fashion or by having their clothing, and thus much of their power, destroyed. However, the first episode has the Absurdly Powerful Student Council flat-out executing one of the students, which ended up being the only explicit death during the course of the show until the Big Bad and The Dragon kill themselves in the last episode. This example is so extreme that viewers pretty much have to ignore or rationalize it (maybe the student wasn't quite dead?) in order to accept the council becoming antiheroes later on.
Assassination Classroom has been very consistent over its run — with one glaring exception in the first chapter. Knowing Koro-sensei like we do now, it's unthinkable that he would ever threaten his students' families.