Jack-of-All-Trades - Hayate and Hinagiku are both this. Each has an arsenal of mundane skills and knowledge that enable them to solve just about any problem they come across in addition to being highly skilled combatants each able to take care of themselves even against demons and monsters. Their skills even seem to be complementary, since whenever one of them doesn't have an answer or is unable to do something, the other will invariably know/be able to do exactly what is needed without fail. Naturally, they are to go-to characters for the rest of the cast to go to when they are in a fix.
Japanese Honorifics – Hayate uses the -san title for everyone, in keeping with their high-class standing, except Nagi and Sakuya, who he calls 'Oujo-sama'. Nagi is his master, but there seems to be no forthcoming explanation for why Sakuya is included. He has also at least once called Nagi ‘Nagi-sama’.
Hayate seems to be rather fickle with Nishizawa though; sometimes he will use ‘Nishizawa-san’ or sometimes not use any honorific at all.
He also gave Athena the nickname 'A-tan' when they were children, and still calls her that.
Hinagiku once commented on this when he refers to Athena as this after he is "rejected" by her at the end of the Greece Arc and notes that it is odd given the circumstances. He then suggested that he could start calling her Hina-tan, to which she instantly gave a deadpan 'I absolutely refuse'.
There's also Isumi who uses Hayate-sama which at one point enabled Hayate to figure out Isumi's involvement and mission in a certain matter solely because only she ever calls him that.
The Jinx - Hayate again. Particularly with money, but it doesn't really matter. Bonus points for also being Born Unlucky.
Woe to any character that somehow becomes lucky, as Hayate might appear to inadvertently ruin their good day. If money is ever involved, Yukiji may also show up, but Hayate on his own can be quite worrisome to a Genre Savvy character.
Just a Stupid Accent - In the dub mainly, the maids have British accent while Klaus and a few others has German accent.
Just for the Heli of It - Isumi keeps trying to convince her friends to ride with her in her helicopter as a means of travel, despite the lack of need to use it. Considering this is her fifth helicopter in as many days it's no surprise her friends prepare more normal methods of travel.
Lemony Narrator - The narrator frequently argues with the characters, snarks at the plot, and was once accused of murder by Nagi. And he has the voice of Norio Wakamoto. He even seems to develop as a character, starting out with mere sarcasm and eventually developing an utter disdain for the show's cast. In one episode, when the gang takes a cruise and Nagi complains that the Titanic-sized ship is too small, he says, "God, I hate rich people. I hate them so much." It gets better in the Animax dub where he has a British accent and sounds like Tom Baker!
Lethal Chef - Nagi, who (among other instances) declared her failed attempt to make Valentine's chocolate "A chocolate-covered iron pot!" to save face.
Limited Social Circle - Hinagiku, Miki, Risa and Izumi are all friends, and are almost always seen interacting with each other exclusively. As the story continues, the social circle expands a little, to include Hayate and Nagi and eventually several others, but still rather limited.
Isumi, Nagi, Wataru and Sakuya share the same dynamic, being childhood friends, they are hinted to have grown up together, mostly because their parents were all friends/family as well, and have limited interaction with anyone else. Isumi is a Cloudcuckoolander, Wataru spends all his time not at school trying to keep his business running, and Sakuya goes to another school supposedly. Nagi started off being a Hikikomori but has begun to start expanding her social circle because of Hayate's influence.
Lightning Glare - Nagi and Ayumu do this in episode 20 of the first season. Interestingly, the spot where their sparks meets starts a small fire.
Limited Wardrobe - Hayate, Maria, and Saki are rarely shown wearing any other outfits other than their uniforms, save for some occasions. And also Wataru may count as well.
Lolicon - The design of the characters around Nagi's age have this clearly in mind, and have even been lampshaded by Maria and some other characters in the manga.
Averted by Hayate himself - one of said characters confesses that she likes him, and his response is "hey, kids like me; maybe I should be a teacher"...
And then there's chapter 160 featuring fanservice shots of 10-year-old Maria.
Lampshaded and mocked in a side-chapter where 10-year-old Maria gets a love letter and Makimura automatically assumes it must be from a Lolicon pervert. Maria warmly and gracefully states that she shouldn't be so dismissive of other's feelings, and that someone put their heart into this letter... and in the very next scene is shown burning said letter because she read it and found it really was from a Lolicon pervert.
When Wataru and Saki go to Las Vegas and meet up with Wataru's mother, Mikoto, her butler is explicitly stated to be a Lolicon to explain why he's not doing anything against Sakuya being used as a pawn to force them into a gambling situation.
Longing Look - Save for Ayumu, none of them have had the nerve to actually confess though, so their lack of romantic knowledge ends up with it just being played for UST.
Actually, Ayumu is only the first (and she did so twice) of three to have confessed, Athena (though she then 'rejected' him, and then denied it as Alice) and Luca have as well (although Luca confessed to Hayate under the impression that he was female and added the condition that 'if he were a guy'). Hayate is just to clueless to have picked up on any of them.
Loophole Abuse: In episode 1 of season 2, Klaus makes a bet with Hayate that if Nagi fails to win the upcoming race, he would be fired as her butler. Despite everything he tries, Nagi finishes in second place. When Klaus refuses to reconsider firing him, Nagi says she'll fire the former as well, since a head butler's subordinate failing a task falls on him as well. Maria agrees with her, having also been asked to do a humiliating task by Klaus in the previous episode as well. Klaus then decides he'll give Hayate a second chance to save his own job.
Loser Son of Loser Dad - Hayate is a heroic inversion of this plot. Ayasaki-Dad is always stealing money (he even cops to it), run con businesses and has been stated to have two large debts, one to the 'very nice men' and one to Wataru's video store. But Hayate is the hero of the manga, and his brother is stated to be a hero, even going to rescue Athena from the devil.
The Lost Lenore - Although not confirmed to have died, the original Katsura sister's parents are this to Hinagiku after they abandoned her and her sister before the story started. It's part of the reason that she's so hesitant to acknowledge her true affections for anyone, including her love interest, is because of how much their loss hurt and she's afraid of having to suffer loss again because of it.
Love Bubbles - Happens a lot with different characters, and is even used in the third ending theme in the anime.
Love Confession - Averted with Hayate, whose 'kidnapping' of Nagi got interpreted as this and started the entire series. Isumi was technically the first to play this straight when she told Hayate she liked him.
Three different characters do this later, with five seperate confessions. None of the characters are attached to anyone.
Ayumu confesses, twice actually, the first time she's actually rejected, though it doesn't deter her affection.
Ayumu eventually confesses a second time, actually at Hinagiku's insistance. Though initially she gives Hayate 'obligation' chocolate as part of Valentines' Day, Hinagiku insists she talk to Hayate again and give him the chocolate she made for him, telling him that he doesn't need to respond yet. Though he hasn't rejected her again, he has made it clear that he has some affection for her, making this the closest thing to an actual confession and acceptance.
Hinagiku has attempted a confession-of-sorts when Hayate has taken her out on a date, but given her fear of loving someone, she does it just as a train passes by, and so he can't actually hear the words.
Hayate does this as well, for his '10 years ago girlfriend', first in front of Hinagiku (again), and then directly to the girl he loves, and she responds in kind, but then sends him back to his master, which he takes as a rejection.
As of a 300+ chapter, [[spoiler: Athena expy Alice actually states that she has no affection for him. What this means in light of earlier events hasn't been fully played out.
Finally after 330+ chapters Wataru confessed to Isumi for real and didn't try to play it off as a joke, however he also went with "loved" in the past tense much like Hayate did to Athena, and seems to have moved on...a very good day for Wataru/Saki shippers given how the two were acting for those two chapters.
And now Luca/Ruka has confessed to Hayate and even caught him off gaurd to kiss him.
Love Dodecahedron - Obviously, most of it centers around Hayate and his Unwanted Harem, but Wataru is also starting to develop a harem of his own, and there are even a couple of links that don't involve either of them.
There are also a few links that link both Hayate's and Wataru's harems together. At this point, there are enough polygons to make a full-fledged sphere.
Love Epiphany - Several, though one of the most notable is when Hinagiku finally admits to herself that she's in love with Hayate at the climax of her birthday arc.
Love Hurts - One of Hinagiku's fears is based on this, and it's implied that her fear of heights extends from this.
She's afraid of loving someone because her parents left and her older sister has turned to drinking after making sure that Hina doesn't have to deal with the debt and has foster parents, thus she's afraid of loving anyone again, in an effort to keep from getting hurt by them. She may have even turned to her Tsundere personality because of it.
Her admitting (to Ayumu) that she does love Hayate has been shown as an effort because of these fears.
Love Letter Lunacy: In episode 48, a lot of Ship Tease is done with Hinagiku and Hayate. Both receive what they think is a love letter written by the other, telling them to meet outside the kendo training hall after school. They are both stunned to see each other there, and wonder if the other did write that letter. It turns out it was written by Koutarou Azumamiya, a minor character in love with Hina, and intended to defeat Hayate in front of her to score some cool points with her.
Love Makes You Dumb - All over the place given the seemingly contagious case of Cannot Spit It Out that the entire cast has (save Ayumu and now Wataru and even once Hayate himself. However, almost every relationship seems to have this to some degree or another.
Nagi has obvious done some very stupid things in her plans to "rekindle" her relationship with Hayate, most blatantly when she agreed to let Gilbert 'kidnap' her in volume 3.
Ayumu jumps to some pretty strange conclusions herself regarding Hayate and has devised almost as many plans as Nagi that have little basis in logic.
Kaoru-sensei also has this problem in his hilariously bad attempts to woo Yukiji and his continual failure to understand exactly where he went wrong.
The biggest offenders by far, however, are Hayate and Hinagiku. Hayate already does some pretty stupid stuff for the girls in his 'harem'. That said, his IQ drops a few extra points whenever Hinagiku is involved, especially if he thinks he did something to make her mad. This usually results in him putting his foot in his mouth, such as telling Nagi that he wanted to learn a Finishing Move to impress Hinagiku. Hina, for her part, also has frequent lapses in logic where Hayate is concerned, which usually end up mercilessly snarked at by the narration boxes. It gets to the point where some of the issues that crop up between her and Hayate only make sense in her mind, such as not wanting to move into the Violent Apartments with him apparently due to her idea that the two of them will act like a couple of newly-weds (with her as the husband leaving for work and Hayate as the stay-at-home wife). Even the narration boxes point out that this has no basis in reality.
Love Triangle - Sonia -> Wataru -> Isumi. Also, Nishizawa -> Hayate <- Hinagiku, as a subset of a much weaker Love Dodecahedron that includes Nagi and Maria (which forms the initial love triangle).
Are you sure that second one hasn't turned into a type 13? Or perhaps even weirder still, a type 9 (see above)?
Luminescent Blush - Most of the cast is quite good at this, especially when combined with Love Bubbles and Cherry Blossoms. However, the Queen of Moe, Hinagiku, seems to do this far more often than anyone else and usually much brighter.
And often with wording fumbles atop the blush. Hinagiku and Ayumu pull this off (all at their separate times) along with Hayate himself during his stay at the Katsura household.
Hayate in particular gets an absolutely epic one in the manga at least when Maria (in 'disguise') and Hayate are riding the clock tower elevator and Maria teases him by asking if he is in love with the Student Council President (i.e. Hinagiku). Hayate's reaction consists of a literally Luminescent Blush, much stammering, apparently trying to deny it by listing all of Hinagiku's good qualities and finally being unable to speak coherently. It makes This Troper laugh every time.
Mad Scientist - The very cute meganekko inventor of Eight and the other killer robots. Sometimes ventures into being FOR SCIENCE!!! (as far as weaponry's concerned), if she wasn't kept grounded by her quest for funding.
How an irresponsible and immature drunk like Yukiji Katsura, Hina's older sister, hasn't been fired from her job as a teacher is beyond any conceivable logic, but luckily for her logic doesn't apply here. Case in point: the superintendent is far crazier.
Hayate's parents probably qualify too, since they don't seem to even realize how their horribly selfish actions affect other people, especially Hayate.
Marry Them All - Proposed by Nishizawa once in regards to herself and Hinagiku. Oddly she left out Nagi, who she knows is also in love with Hayate, although she might change her mind as they start becoming better friends. Equally strange is the fact in all of the discussions Nishizawa and Hina have had about Hayate she has never brought up the fact that Nagi is also their love rival and thus Hina remains as unaware as Hayate on the matter.
While the option played straight is very unlikely to happen, there is an interesting variation that has a chance of happening, that being Nagi's new apartment (maybe after a possibly foreshadowed expansion) eventually having all the Haremettes move in with Hayate continuing to act as the "butler included" and thus sharing him.
Masculine Girl, Feminine Boy - Hayate and Hinagiku, part of the reason Hinagiku was dubbed female!Hayate and they're considered mirror counterparts. Hayate has a very girlish face, more so as time goes on, as well as a traditionally feminine skill set (cooking, cleaning, and sewing among other things) which makes girls around him feel as if their femininity is threatened. He is also quite sensitive at times, and in the beginning was brought to tears quite a few times by acts of kindness. Hinagiku was very much a tomboy when first introduced. Her position of authority as Student Council President and her outstanding athletic skills were both amplified by her aggressive and take-charge demeanor. Unlike Hayate, she focused on being decisive, and wasn't really afraid to use force to solve an issue.
Part of what makes it an interesting case is the change over time. Hinagiku has changed the most, becoming much more feminine as part of her Character Development, acting more dere when flustered instead of covering it with aggression, acquiring a sense of feminine modesty that Hayate tried to impress she was lacking, and generally sliding more to the 'feminine' side of the scale while still remaining 'masculine'. Perhaps her biggest 'feminine' factor is worrying that she isn't that feminine, though luckily for her Hayate seems to like her 'masculine' characteristics. Hayate is more inconsistent with this, sliding from more 'masculine' such as taking on responsibilities himself and trying to be a strong figure to protect and help others as well as going awfully far down the 'feminine' side of the scale (the crossdressing really hasn't helped him much). Oddly enough, Nagi's and Hinagiku's fantasized version of him is typically more on the 'masculine' end of the scale being confident and cool, though one of Hina's most recent moments had Hayate almost like a stay-at-home wife, though he remained sparky and 'cool'-looking. As much as she claims that he can be a dork, it seems that Hinagiku actually does like Hayate a little on the 'feminine' side of the scale as well.
A Match Made in Stockholm - At least kidnapping was Hayate's original plan, it's subverted in the end however. Despite his decision to "become a devil" to get the money to pay off the Yakuza chasing him, every time he gets the chance to do something evil he thoughtlessly does something nice instead. The guy's so nice that Nagi took his declaration of kidnapping as a confession and a request to elope...and considered it. No word yet on if they are going to be the Official Couple or not, but it gave us a series.
Meet Cute - Hayate with both Maria and Hinagiku. Maria had a classic example with running Hayate over on her bicycle before rushing over to help him. Hinagiku first met him when she was having trouble getting down from a tree and jumped before Hayate was ready to catch her, leading to her foot landing square on Hayate's face and sending him sprawling. Maybe he just likes girls that cause concussions when he meets them...
Isumi gets shanghaied into wearing a maid outfit so that the spirit of a perverted priest can flirt with a maid, fulfilling a desire that's keeping said spirit from moving on to the afterlife. Although, that reason turned out to be an April Fool's joke by the priest.
Memento MacGuffin - Though Hayate doesn't know of its significance for quite a while, he's given the King's Jewel/Stone of Bonds by Mikado, it reminds Mikado of his daughter, who appears to be the original one who found the stones (she's dead and he seems to want her brought back). It's called the Stone of Bonds by Maria and Nagi, and it reminds Nagi of her bond with Hayate. Eventually Mikado decides it's useful as a mark of inheritance for the Sanzenin fortune.
It's also a stone that Athena and Midas need to reopen the doorway to the Royal Garden. Multiple uses for a single item that didn't seem particularly noteworthy at first.
Mind Screw - Nagi's manga could probably count. It is so bizarre and convoluted that only the Cloudcuckoolander Isumi understands what the hell is going on. But Nagi's manga has nothing on Isumi's own creations. Ohmygod That last one even has a punchline...
Misplaced Wildlife - Tama's backstory is that Nagi found him as a tiger cub in Africa, but there are no tigers in Africa. Upon having this fact pointed out by fans, the author admitted in his notes that he didn't bother with research, and hangs a lampshade on this apparent inconsistency in a later chapter. Apparently, in addition to tigers, traditional African wildlife includes pandas, unicorns, and what is clearly a person in a dragon costume.
Then again, in the long run, it wouldn't have mattered too much considering the series. Besides, it's funny either way.
In an episode of the anime the same mistake is repeated when an elephant is shown in the Amazon.
Mistaken for Gay: In episode 43, Hayate is saved from drowning by Klaus. Hayate has a Bishie Sparkle when he thanks Klaus, which Nagi is able to see, and Klaus, while acting cool and trying to downplay his heroics, also ends up with some Bishie Sparkle as well. Nagi immediately assumes the worst, and tells him not to do that, which confuses Hayate regarding what she was referring to.
Moment Killer - Hayate and Hinagiku. Pick a moment. Any moment. The universe indiscriminately uses any nearby character to kill the mood, even resorting to using Those Two Nekos Tama and Shiranui. Should Hayate and Hinagiku be alone together, one of them will invariably self-destruct - the most brutal so far being Hayate interrupting Hinagiku's attempted confession by declaring that he loves Athena.
Wataru also has problems with this. On several occasions he's blurted out his feelings for Isumi and she's overheard - and every time he frantically tries to revoke it. He's so consistent and adamant about this, Isumi actually believes he was just joking.
Nagi often tries to have romantic moments with Hayate, but the poor dear just can't catch a break. Certainly doesn't help that she's not even on his radar.
This is Yukiji's modus operandi where Kaoru-sensei is concerned, even though she openly acknowledges that he'd be a pretty good catch.
Mundane Luxury - Hayate deals with having found a job as the Sanzenin's butler as living in luxury in the beginning, having had to work extremely hard to barely survive on a meager living up to this point.
When he's given a million yen so that he can live outside the mansion for three days, he's told to spend all of it and spends the next few panels explaining that he could live in luxury for the next year with that kind of money. Of course, he's spent it all before he even finds a place to stay for the night.
Mundane Made Awesome - Chapter 282, where Ayumu is trying to trick Hayate into asking her when her birthday is (it's that day), while Hayate is trying to avoid the subject like the plague (they have a surprise party planned for later), is played exactly like a fight scene, complete with side characters commenting on the tactical choices.
Murder Is the Best Solution - This was actually used by Hayate during the Segawa Arc where after all the jerking around left him in a death match in a lava (magma?) battle arena, he determines - with his usual bright, cheery expression - that everything can be solved if he kills Kotetsu...most obviously for his constant attempts to grope and hit on Hayate. Nobody dies and the former even saves the latter (before knocking the latter out for 'getting ahead of himself') and alls well that ends well.
New Old Flame - Hayate's first girlfriend Athena makes an appearance later in the manga.
Except that, while Hayate still holds a flame for her, it's not clear if she has the same for him. And their former relationship was left at the point of her and/or the spirit possessing her, wanting to kill him.
Never Got to Say Goodbye - The last time five-year-old Sanzenin Nagi ever spent with her ill mother was in a tempered-tantrum argument... and this would go on to shape the abrasive person that she grew up to be.
Nice Guy - Ayumu Nishizawa is clearly a nice gal, paired with the fact that she's a normal person in a world where most of the rest of the cast are Ojous really makes Hata have to work to keep her relevant, and he does.
Nigh-Invulnerability - Hayate. Would be Made of Iron except it's taken to extremes with no explanation given besides his childhood being inhuman. There's an explanation now. He was "given the body of God" via a spell by Athena.
There's the fact that his name's on the series, too, which is indirectly lampshaded often enough.
Ninja Log: Klaus does this in episode 36 of season 1.
Ninja Maid - Although she's clearly a candidate for it, Maria seems opposed◊ to being known as one.
No Fourth Wall - All characters are aware they are in an anime (or manga), referring to censors, commercials, pages, the Narrator, the audience... in fact, the show seems to take the very existence of the fourth wall as a personal affront, and pounds it into rubble at every opportunity.
Not so much in the second season.
No Guy Wants an Amazon - Hinagiku worries about this in an internal monologue during the beach volley ball match during the Greece Arc, fearing that going all-out on an annoying Gilbert would lead to Hayate being turned off by her lack of femininity. Aside from the fact that Hayate has already had plenty of opportunities to see Hina kick ass, she never had anything to worry about in the first place since Hayate clearly likes that "cool, confident, action-y" side of her.
No OSHA Compliance - Why they have non-safety compliant sections in Sanzenin mansion is anybody's guess, such as the seemingly nuclear-powered boiler which can get a meltdown when someone pressed the wrong button.
No Sense of Direction - Isumi, though it turns out that at least part of it is because local spirits routinely interrupt her trips to ask her to fight demons troubling them.
That happens 2-3 times per year. She's as bad as Zoro.
No Water Proofing In The Future, subverted - When one of the butler robots attacks Nagi, it shrugs off a water attack by Hayate, only to be later defeated by a handful of silver cutlery and a generous helping of electricity.
Non-Standard Character Design - Hinagiku was actually drawn like this in the earlier chapters and parts of it lasted as long as the Greece Arc. It's especially noticeable in her introductory chapter where she was drawn in a much more...flowery style that is heavily reminiscent of Utena, which seems to be one of Hata-sensei's inspirations for her character and some elements of the plot. Her eyes and hair especially were different at first, but as the art style for the series has become more Puni Plush her design has become more-or-less the same as everyone else's unless she's being focused on.
Several times, he is somewhat distracted, but still recovers himself before the girl in question even gets over the shock of being seen. Hinagiku and Maria are the only ones who he really plays Distracted by the Sexy straight.
He's not clueless about sex appeal, just not affected by it like normal guys. Pointed out when Miki shoves a magazine in his face, and states that he's the perfect one to take Hinagiku out because of his reaction. And when Izumi gets possesed and Hayate comes in on her with Hinagiku in a suggestive pose, his reaction is significantly less than you'd expect from a normal male seeing it.
Not a Date - A couple of times, but not as much as you might expected from a romantic comedy series.
One humorous occasion was when Nagi set up Hayate and Maria on a fake date to lure out a Yandere stalker. She even wrote scripts for them.
There was also Hayate and Hinagiku's date to the movies. Once they finally made it into the theater and their hands touched on the arm rests, to two of them finally realized that what they were on could be considered a date. When things fall to pieces (since they were set-up for failure in the first place), Hayate takes her to totally-not-Disneyland-Tokyo where the matter of it being a date is brought up again. This time neither denies it and instead Hinagiku changes the subject to continue the technically-acknowledged date.
A second, semi-acknowledged date would be him taking her out to a very fancy dinner one evening in Greece to show his appreciation for all of her help. This time Hina doesn't deny it at all and actually spends most of the date trying to confess her feelings for Hayate.
Kazuki Nishizawa also took Nagi out on a date, which Nagi was in denial of the entire time. However, she still felt guilty over the fact that she really did have a good time, causing her (delusional) imagination to perceive Hayate's normal behavior as him being hurt that she "betrayed" their "relationship".
Oedipus Complex - Apparently, Hayate greatly resembles Nagi's mother... despite being male. So this is gender-flipped and played straight.
Official Couple: Unless Kenjirou Hata is trolling the fandom, Chapter 318 seems to show that Wataru/Saki may have become this. Isumi, who Wataru had a big crush on, helps him realize that he likes Saki the most. He later says that he well stop going to Hakuo (he only went there for Isumi) to focus on the family business and asks Saki to promise to stay by his side, with both blushing furiously.
Chapter 318 does nothing for the actual pairing though, and the implication is that the relationship between Wataru and Saki seems to be more of a mother/son one. Whereas Wataru/Sakuya seems to be gaining speed, with his apparent abandoning of Isumi-persuing. The fact that Sakuya gave him the money for the entire arc to start, and then helped him find the stolen money indicating that it's not one-sided.
The arranged marraige between Wataru and Nagi has still yet to be clarified, it was implied that it was for the Sanzenin inheritance, which Nagi is not going to get anymore.
Offscreen Inertia - Referenced when Hayate wonders if maybe Izumi is still on Mount Takao after having been forgotten there by Yukiji since she hasn't been seen since.
Ordinary High-School Student - Episode 46 has Nishizawa showing Wataru and Saki around her "completely normal High School" which is filled with "Completely Ordinary High School Students". That is to say...it's filled with heroic delinquents and time travelers. This was the same school that originally produced Hayate...
Lampshaded in the very first issue of the manga when Hayate runs into some other students (which also hangs a shade on Hayate's playing Mister Exposition):
Hayate: Ah.. well, well, if it isn't my classmates from my ordinary public high school.
Student: Sorry for being ordinary.
(Are you explaining something?)
Hayate falls off being normal once his past is revealed, and Ayumu has been given a younger brother, but she's still really the only one who fits.
Otaku - Nagi. Chiharu as well. Hayate is not, but he definitely knows just as much as Nagi when it comes to otaku subjects. He will even talk like Nagi every now and then, which gets lampshaded.
Kayura and her parents, who named her after the Ronin Warriors character.
Our Demons Are Different - According to Isumi, demons are entities possessed by an evil spirit. Anything can become a demon; objects, humans, animals. She repels one that had possessed a horde of rats, and then some rather large ones that had possessed a Koi Herpes Virus that had infected a nearby koi pond and were terrorizing the local kami.
Overtook the Manga - The "Butler Battle" arc in the anime wasn't in the manga, hence the Ultimate Butler Armor disappearing after.