The only henchman that he's particularly mean towards in season one is Lilith and while she's afraid of him, it's portrayed more as him growing justifiably fed up with her continual failure and covering for Eda, and it's further intimated that he's been cutting her a lot of slack prior to this. Even when he betrays her by refusing to cure Eda, it's left ambiguous if he does so out of simple dickishness or some deeper reason, and it seems more like a change from his original plans than something he intended to do from the start. He's perfectly polite towards his other underlings, is somewhat accepting of slip-ups and mistakes, and actually seems to reciprocate Kikimora's feelings towards him, comforting her over the losses taken in the season finale and calling her "Kiki" in an obviously affectionate manner. Compare that to season two, where he's a terrifying Bad Boss who doesn't hesitate to demote or punish his mooks at the slightest failure, hardly treats his Quirky Miniboss Squad any better, and views Kikimora in particular as an annoying but mildly useful pest.
While his goals aren't revealed in season one, Belos' behavior in general and the way he talks about his Evil Planreally makes it seem like he was originally intended to be more of a genuine Well-Intentioned Extremist with an understandable motive than the hateful Knight Templar determined to destroy the Demon Realm out of misguided revenge that he is established as in season two. Aside from the aforementioned kinder treatment of his henchmen, he's also portrayed as somewhat laidback and willing to take short-term losses for long-term gains, being more ambivalent than anything to the Owl House residents and Luz especially given their connection via the Stable Time Loop and both being human, and generally talks like he earnestly thinks what he's doing is for the good of both realms. This even extends out-of-universe; season one-contemporary promotional materials, such as an interview with Matthew Rhys, tended to frame Belos as being Not Evil, Just Misunderstood and having Hidden Depths beneath his tyrant persona, something that's somewhat believable in season one but downright laughable to suggest in season two onwards.
Given what a famous, public, and propagandized (if secretive) figure the Golden Guard/Hunter is established as in the second season, being Belos' right-hand man and supposed nephew who rarely leaves his side, it's a little weird in hindsight that he doesn't appear or get mentioned at all for most of season one, and when he does it's at the very end as a Sequel Hook that makes him out like a shadowy and ominous spy who observes or eliminates potential enemies for Belos. In fact, as noted above, Kikimora is portrayed as being Belos' highest ranking minion and acting accordingly; a far cry from the petty, self-important, bootlicking glorified bureaucrat that she's shown as in season two.
In the first season when Owlbert was the only Palisman regularly seen (aside from Lilith's, who never left its staff in that time anyway), the staff was shown to be a separate piece from the Palisman, with Owlbert frequently seen leaving the Owl Staff vacant when he animated. Later on, when more characters were shown with their own Palismen, the staff became an extension of the Palisman that would disappear when the Palisman became animated. Owlbert himself would later show this during the fight in "O Titan, Where Art Thou".
It's revealed in season two that members of the Emperor's Coven have to give up their Palisman upon joining, which makes Lilith's possession of her staff while Head Witch during season one all the more glaring.
When Eda tells Luz that her Owl House has an excellent security system, the two of them enter it via Hooty opening his mouth wide into a doorway that they walk through, implying that Hooty will only grant access to people who are supposed to be there. This is never shown again; in all subsequent episodes, the door just works like a normal door, and the security that Hooty provides is acting as an extendable doorknocker capable of single-handedly beating up potential intruders, though he does open his mouth extremely wide to serve as a pit-fall trap during Eda and Lilith's Grudgby game in Episode 17.
Towards the start of the episode, Luz puts some batteries into a portable television and turns it on. The inhabitants of the Boiling Isles are mystified by it, with one asking if they can "eat the tiny human inside." Later episodes would demonstrate the existence of crystal balls that are functionally identical to televisions, making their reactions to the television seem strange in hindsight.
When Luz hugs Eda, she reacts as if she has no idea what a hug is, and again two episodes later she mentions being confused by Luz's "parallel arm thing". However, later episodes would make it clear that hugging is a normal practice on the Boiling Isles. While Eda being uncomfortable with hugs at first makes sense given her closed-off attitude, her not knowing what hugs are at all doesn't make much sense.
Luz is unable to move a lever to help free some prisoners because of her "weak nerd arms" in total contrast to later episodes, which tend to portray Luz as being a fairly athletic tomboy despite her stereotypically nerdy interests, a fact called to attention in episode 17 when she casually lifts Amity into her arms and carries her with zero effort. While it's theoretically possible that she might have become stronger over time, it can't have been more than a few months between episodes.
The pilot in general portrays the dystopian aspects of the Boiling Isles in a much more exaggerated, cartoonish light that's a lot more explicitly parallel to Luz's struggles against conformity on Earth; the mooks are significantly goofier and depicted as arresting people for being mildly weird (like believing in conspiracies) amongst other things. Later episodes tend to portray Emperor Belos' government as more subdued and realistically corrupt and controlling, with the main focus being on how they rigidly partition magic and brutally crackdown on dissenters.
Eda and King make a pointed distinction about Adegast being a "wizard" rather than a "witch" (whether or not Adegast really was one). Later episodes show witches as the species the magic-using humanoids of the Boiling Isles belong to, and never refer to any magic users as "wizards" again.
Eda explains that witches get their magic staffs through school. This was later retconned, with teenage witches instead carving or adopting their own Palismen as a coming-of-age ritual. While Luz's classmates do get their Palismen through school, "Hunting Palismen" makes it clear that this is not common practice.
Adegast is casually killed off in the episode. The show avoids killing off characters after this, with all the upcoming deaths (Flapjack, The Titan, and Belos) being in Season 3.
"I Was a Teenage Abomination": Principal Bump's order for Willow to open up her Abomination-Luz in disguise-to see its contents paint a much more devious and malicious character than what the show would later establish as not evil, but misguided and oblivious due to the harsh world he lives in.
This episode is technically the debut of the Construction coven head, Mason, but nobody reacts to his presence despite the show later establishing that coven heads are a very famous group of witches, meaning someone should've recognized him at the very least. The creators later explained that at the time they hadn't planned for him to be the head, and decided to use him instead of coming up with a new design, while hand-waving that in this episode he hadn't yet been promoted.
The Construction Coven is shown using "power glyphs," which are already treated as distinct from Luz's glyphs, to magically construct buildings in "Covention" which are never seen again and construction magic being done with spell circles as with all other covens.
Amity mockingly calls the fully sapient King Luz's "pet", implying that non-witch demons are discriminated against. This isn't seen to be true in later appearances.
Amity is portrayed as Lilith's protege in this episode, being groomed by her to become a member of the Emperor's Coven. This relationship is never mentioned again after this episode, and the two of them never interact with one another for the rest of the series. This, and her lines about "fostering new generations of powerful witches into the world" in the same episode, seem to be The Artifact from an early plan where Lilith was going to be Headmaster of Hexside instead of Principal Bump — meaning her close mentorship of Amity, and Amity's "Top Student" status at school, would be one and the same plot point.
"Lost in Language": Edric and Emira bring Amity's lunch in a very childish pink bag, claiming that it was sent by their mom. One would think that Odalia is an Amazingly Embarrassing Parent, who ruins Amity's attempts to look cold and stoic, while that is as far from the truth as possible.
"Once Upon a Swap": This is the only episode in the series where you'll hear Boscha refer to Luz by name rather than calling her "human" like most of the cast outside of Luz's friends.
"Understanding Willow": While complaining to her parents about her new "friends", Amity calls both Boscha and Skara mean. Later episodes would establish Skara as more of a neutral blind follower of Boscha, and eventually make it clear she's pretty chill when Boscha's not around, with Boscha being the one who's truly mean.
"Agony of a Witch": When Luz, Gus, and Willow steal the Healing Hat and mess around with the other relics, Belos' voice echoes around them, whispering "I will know." This action heavily implies that not only can Emperor Belos telepathically see everything that goes on in the castle, but he can speak to anyone no matter where he is. Come Season 2, and secrets such as Flapjack and Raine's plan are out in the open within the castle, yet Belos doesn't catch on until later.
"Separate Tides": Watching this as someone's first introduction to the Golden Guard can be quite disorienting, as he's portrayed as a legitimate, no-nonsense threat with a little bit of a sense of humor, compared to how the rest of the series would portray him as a dorky teenager who's way in over his head regarding his status and power.
