It looks like, from the start, this will be a pretty funny anime. Then you see the very noticeable, blinking arrow pointing at the Renaissance vase. Even THAT is funny, and it's just a background thing.
On the same note, when all of the lights finally turn on and turn into the kanji for 'female'. When Haruhi comes out in the female uniform, cue Tamaki's hilarious reaction.
In Episode 1, Haruhi is trying to think of a word to describe Tamaki, who is being his usual Large Ham self. She manages to think of a word that describes him perfectly and with brilliant comedic timing, says it JUST as Tamaki sticks his head in. His response? The Corner of Woe.
And what is the word? "Obnoxious."
In Episode 1, Tamaki twirling Haruhi around in a hug while blushing when he thinks that what she said is cute.
This line from the dub, especially the way Luci Christian says it with a completely deadpan tone of voice:
Honey-senpai: [upon seeing Kasanoda with cat ears] Cat monster.
One (of quite a few) is the introduction of Umehito Nekozawa's baby sister Kirimi:
The maid, describing how Kirimi knows all these terms and ideas.
Maid: We've tried to keep her comforted by reading her bedtime stories about princely characters like her brother... but we ran out of stories, so recently we decided to start reading her shoujo manga that had princely characters in them, and I'm afraid she's become completely addicted.
Later in the manga, we find out that Kirimi has become just like her brother. Barring how adorably silly this is, it also means that all the attempts to make Nekozawa princely were completely pointless.
Renge's attempt to make Nekozawa-sempai princely involves putting a blonde wig and dress on Tamaki's ugly teddy bear and having Nekozawa talk to it.
Nekozawa: That doesn't look anything like her! Renge: (cheerfully) Look at her through the eyes of your heart! (angrily) THE EYES OF YOUR HEART!!!
Haruhi begging off spending any more time with Kirimi, with a flashback to Kirimi making her read a mountain of harem mangas.
When they crossdress very badly in an attempt to convince Haruhi not to join the Zuka Club. Even the normally deadpan Haruhi was rolling on the floor laughing to the point of crying! See it here.
Again from the first episode. Honey drags Haruhi farther into the room, calling her "Haru-chan" and wanting to play with her. She says "Thanks but I was just looking for a place to study..." and then she registers what he said and roars "AND WHO ARE YOU CALLING HARU-CHAN?!"
It becomes more hilarious when you realize that THAT'S what pisses her off, but everyone mistaking her for a boy and Tamaki even saying she's openly gay doesn't get so much as an attempt at correction.
From Episode 5, the twins having a huge fight which involves throwing stuff like tables and chairs and eventually Honey's stuffed animal Usa-chan. Honey then runs after Usa-chan and gets thrown around too.
Later, in the refectory, the twins keep accidentally ordering the same thing for lunch. Honey tries to defuse the situation with cake, but gets distracted wondering if he can have some too, and how to divide the strawberry on top, while the twins stand there with growing irritation. Mori just picks Honey up and carries him away, bluntly telling him "You're just making things worse, move along."
When Tamaki notices Haruhi in the refectory, he randomly sprouts a wagging dog tail out of sheer delight. Then her mention of boxed lunches leads to a vivid fantasy involving Haruhi as a lovey-dovey housewife making a heart-shaped bento for Tamaki.
Tamaki: I don't care if my boxed lunch is in an embarrassing heart shape, I will eat it! Kyoya: I have no idea what you're talking about, but it's evident that your fantasies are completely incoherent.
The twins eventually end up throwing things again, and Honey yet again becomes a projectile, followed quickly by Mori, and Tamaki, with Haruhi very quietly getting up, grabbing her bento, and deciding that she's gonna eat in her classroom after all.
Just the action of them throwing things at each other is hilarious to anyone who's used to Western Animation.
In the end, it turns out the entire fight was faked. They just did it to trick Haruhi into letting them come to her house. Her and Tamaki experience Color Failure.
The fact that in the Japanese dub, Haruhi calls Hikaru "meaner" than Kaoru, but in English, she calls him more "mischievous" and it warrants, of course, the exact same reaction, only more melodramatic and over-the-top because of it.
Tamaki eventually gets sick of Shirou's antics and drops a cage on him. Haruhi asks where the cage came from.
Even better when taken as part of the episode's running gag, where Haruhi repeatedly comments on the various crazy things appearing in the room (the cage, Renge's rising-from-the-floor platform, etc.) with an exasperated, "What's with that? This is supposed to be a music room!" It finally culminates in Tamaki revealing a grand piano. When Haruhi asks where it came from, the entire club chimes in: "It's always been there. This is a music room, after all!"
From the physical exam episode, several come: Tamaki attempting to dress up as Haruhi, Honey and Mori getting recognized in their doctor outfits and immediately going "SHHHH!" to Haruhi when she notices, and the twins stripping off their shirts in front of a crowd of girls, igniting a powder keg of Squeeing.
Tamaki's failed attempt at Genre Savvy-ness in the third episode when he says "this anime is a romantic comedy, which means Haruhi and I are love interests!" was funny enough, but the second he turns around and calls the rest of the Host Club the homosexual supporting cast. The look on Honey's face just makes it better; he's looking down at the line Tamaki draws in confusion, as though he has no idea what Tamaki just said.
The episode where Renge first appears. She does a little rant about how the main cast all look like characters in a game she plays, then points dramatically at Kyoya and yells "You're my real life Ichijo Miyabi!" There's a moment of silence, then this...
Haruhi: Uki? Honey: Doki? Tamaki: OTAKU! Hikaru: OTAKU?! [cut to a shot of Mori, who apparently has no idea what an "otaku" is] Kaoru: I'VE NEVER SEEN ONE!
Made even funnier in the dub by the fact that Greg Ayres, who plays Kaoru, is a bit of an otaku himself...
Arguably even funnier is that Greg absolutely shrieks his line.
Then there's when she first sees a picture of Kyoya. She declares that she's going to marry him, packs her bags while getting changed and then leaves on a plane, all in under 30 seconds (not a cut from one of those to the other, but in real time). All the while her father is completely speechless.
Another from the episode with Renge. They're shooting a movie with everyone in the stereotypes she's assigned them. Honey is doing his "bad boy" thing, and then breaks down and runs into Haruhi's lap, wailing "I'm sorry, Haru-chan! I can't do it!"
One from Episode 2. After Haruhi explains why her hair is styled like a guy's, she says "I don't really mind looking like a dude, you know?" (In Japanese, she refers to herself using "ore," a male-only pronoun). Tamaki snaps.
Tamaki: A GIRL SHOULD NEVER REFER TO HERSELF AS A "DUDE"! ('A proper lady should never use "ore!"') MAMA!! Haruhi's using those dirty boy words again! (sinks to his knees while sobbing into a handkerchief) Kaoru: [deadpan] I'm sorry, but who is "mama"? Kyoya: Based on club position, I assume it's me.
Another from the same episode as above. After Haruhi ticks off Tamaki (again) he grabs a trunk full of stuff and pulls out a large picture of Haruhi dressed like a girl. While telling her to listen to "daddy" (him) he then hauls it over to Haruhi and tells her that "Daddy wants you to go back to the way you were!" Haruhi then explodes herself and screams "DON'T BLOW UP MY PHOTOS WITHOUT ASKING ME FIRST!"
One from Episode 8. After Haruhi and Tamaki fight, there's the part with the crab legs (which involves Tamaki getting hit with the sound effect speech bubble, Tamaki discovering Kyoya and Haruhi in an awkward situation, and when the rest of the cast comes in as Tamaki has Haruhi blindfolded with earplugs so that she doesn't have to hear or see thunder and lightning.
Mori when he's sleepy. Just...Mori when he's sleepy!
From Episode 21. Mori's deadpan no-inflection "I'm Frankenstein" followed by Honey jumping at the class rep with a giant pumpkin on his head yelling "I'm the wolfman!" then the subtitle that says "Wrong".
At the beginning of the "Twins Fight" episode, Hunny's lampshading of Tamaki's ability to pull a frilly pink dress from nowhere always leaves me rolling:
Tamaki: [holding the dress to Haruhi's back] What do you think about this, my dear? Hunny: What're you doin' with that dress?
Honey blowing up a military base after his nap was spoiled.
Tamaki's crazy dream of Haruhi living in poverty.
Kasanoda getting Mistaken for Gay by the school's female population. The girls in the school are all pervs.
When Tamaki's father looks dramatically at a spot behind Tamaki, which makes Tamaki turn around... only to see there's nothing there. The chairman proceeds to cheerfully greet Haruhi like nothing happened, while Tamaki goes to his Corner of Woe.
Hikaru and Kaoru introducing themselves to Haruhi's dad, while walking all over Tamaki.
And Haruhi's dad seeing Tamaki on top of Haruhi, and walking over smashing Tamaki into the wall without ever losing his smile.
"Senpai, stop growing mushrooms in other people's houses!"
Then he gets so depressed, the mushrooms grow on him.
Mori gives a detailed explanation as to why Honey will lose to his brother, but Honey wins anyway.
"IT'S OKAY, MORI-SEMPAI, I STILL THINK YOU'RE COOL!"
Not to mention his expression afterwards. And Yasuchika accusing his brother of being AN ALIEN.
His evidence? Every day after school Honey eats three cakes. Three, three-layer cakes, and he does it all in 3 seconds. Then, he mentions that once in the middle of the night, he saw Honey surrounded by five of the same kind of cake and he was just eating it all. Then he made a Slasher Smile while telling him he and Usa-chan would like him to join. And Usa-chan moved by himself. And "Chika-chan" ran for the dickens.
Even made funnier when, earlier, the Twins theorized that this was the reason Chika hates Honey, and it was Played for Laughs.
Haruhi's reaction in the last chapter of the manga to the rest of the Host Club showing up at the door of her apartment in Boston.
How Mori said "fancy tuna", when they were all trying to convince Haruhi to stay.
The first appearance of the Zuka club. Their last exit is spoiled when they all slip on banana peels. And moments before the episode ends, Tamaki also slips on a banana peel while standing perfectly still.
Haruhi's Fear of Thunder when she tried to casually hide in a wardrobe in Episode 8.
And the fact that everybody just ignores this and dramatically crying over how "tear-jerking" this is.
Chika's flashback of seeing Honey eating cake in the middle of the night.
Ritsu Kasanoda, feared next-in-line to lead the mafia, saying darkly: "The truth is, I really like kittens, you know..."
Episode 19 (the Zuka Club's revenge) is basically one non-stop string of funny moments. An anime blog declared it the funniest episode in the show, with the pacing the most perfect.
Matching with the theme of the wealthy and upper-class, the score is littered with classical music. But it plays underneath the crazy antics of the club, and somehow, only enhances the craziness and hilarity, much in the same way the Looney Tunes used to do back in the day. Listen to the OST separately, and proceed to laugh uncontrollably and receive weird looks from your family.
The twins frantically convincing Haruhi that Honey is evil— she refuses to believe it until they tell her his blood type is AB.
Tamaki: That means he's the same blood type as Kyoya!
Tamaki's freaked out reaction to seeing Benio kiss Haruhi's hand in episode 9. As well as his slipping on a banana peel, getting punched by Benio, and upset response to Haruhi telling him she doesn't want to hear about his life.
Later in the episode, after Lobelia performs for Ouran, the camera rapidly pans up the audience to show Benio's fangirls screaming. If you pause at just the right moment, you can see every single Ouran student wearing the same utterly perplexed and confused expression appropriate enough to having just seen a herd of tap dancing giraffes on unicycles stampede past while they're in the middle of the ocean. It doesn't look like they recovered from the shock of it all, as they watch the girls pass, slack jawed, after the performance is over.
In Chapter 27, (whilst trying to recreate a soup) the Host Club try raw tuna topped with mayonnaise and soy sauce in order to see if it'll taste like giant tuna. Their reaction?
Kyoya: [on a mobile phone] Yes, it's me. Find the very first person in the world who said that raw tuna topped with mayonnaise and soy sauce will taste like giant tuna... And immediately banish him from the country.
Later after the Vice Chairman has slipped away, Haruhi makes them eat all of the terrible food they made. They are all sick the next day.
The episode with the Newspaper club. Their president is so sure there's something fishy about the Host Club, and that Tamaki is a mastermind.
From the same episode, Tamaki (after being taunted by the twins) uses his aptly-named "Starlight Kick" on a can and sends the thing sailing away into the sky, never to be seen again.
This hilarious delivery:
Akira: So having a commoner in the club is just another example of the Suoh family flaunting their riches!
In one episode there's a scene where the twins are lying in their (shared) bed in front of their maids. Hikaru pulls off the covers and reveals he's wearing a colorful elephant head on his crotch, that blasts confetti into the air. What really makes the scene is the identical twin maids, who aren't even slightly phased, simply continuing their chorus to declare that breakfast is ready.
In the chapter where Kyoya's managed to find Tamaki's mother, one of the first things that comes out of her mouth is to ask him if he has a kotatsu in his house. Cue big sign of "Deja vu???" appearing above Kyoya. It continues with her asking him about the exact same things Tamaki did when he first met him, all the while keeping a priceless expression on his face as he can't believe how alike they are.
When the Host Club's following Haruhi and Tamaki on their date in Chapter 82, Tamaki at one point flirtingly asks Haruhi to feed him, to which the twins get an epic "You have GOT to be kidding me" expression on their faces. It ends with them throwing a shoe at Tamaki's head before Haruhi gets the chance to do what he asked.
The ending of the manga: Haruhi and the guys finally bite the bullet and come clean about Haruhi's secret to the Host Club's fans, which they do by dolling Haruhi up in a dress and having her dance with Tamaki. To their surprise, the girls aren't thrown for a moment, and on the contrary explain that they knew all along and are totally supportive. When Haruhi's father makes a reference to her being a girl in front of them after Haruhi has left the country, however, they respond with sudden confusion - turns out they'd thought Haruhi was a gay male cross-dresser.
In the manga when Haruhi didn't tell her dad about the parent conference as a little girl. She had quietly got up with her dishes about to put them in the sink when her dad brings it up. Caption: Escape Attempt Failed.
When Honey has a cavity and his attempts to get candy when he isn't allowed any.
Caption: Strategy 3 - Tearful Act
However this fails because Haruhi gives him a chocolate substitute instead. Honey failed to select the correct target individual.
The ultimate revelation that Mori had been acting harshly around Honey because he feels so guilty about not reminding Honey to brush his teeth before his naptime, thus leading to Honey's cavity (and the fear that Honey will get false teeth). Therefore, he wanted to self-punish himself by getting Honey to get mad at him.
The curry scavenger hunt.
Haruhi rushed around to the different stations to tell them that the final location had moved and was out of breath when she got back to hers. It is then that Kasanoda brings up the Mundane Solution:
Kasanoda: Wouldn't it have just been easier to announce it over the P.A.?
Haruhi: Never say that again. [out of breath]
In Episode 23, where Kasanoda runs to Mori in hopes of getting advice to be attractive with his ugly mug and proceeding to unintentionally offend Mori.
In Episode 24, after Kasanoda has discovered that Haruhi is a girl, the twins decide that the best solution is to beat him with a baseball bat until he suffers memory loss. Even funnier, the only reason Kyoya stops them is because it would be "troublesome to cover up crimes."
Tamaki: Kyoya, you've really gone too far this time! Look at me, I'm breathing fire! I'm breathing FIRE! It's the fire of my anger right now I tell you! You've turned the king of the Host Club into a dragon! I AM THE DRAGON KING!
The outtakes from the second episode, with Kanako, from her boyfriend. "It's just a kiss on the cheek, right? You should accept it. It will commemorate you graduation from [host hopping originally] being a total whore." delivered in the same cheery voice to boot.
"What is it now...daddy?" The line is said perfectly, but seconds afterwards J. Michael Tatum cracks up (naturally surprised by the shiptease).
The "really?" at the end of his laughing. It had her rolling on the floor because not even the voice actors could believe this show.
And speaking of Kyoya..."Iiiii hate your face." "Weeeee're out of money." "WE'LL SEE YOU THEN!"
Travis Willingham absolutely losing it over Mori's top-speed intervention during Haruhi and Hikaru's date in the Karuizawa episode.
[in character] Bad idea. ... [busts out laughing] Oh my god he just comes through and like — BOOSH, and he's still wearing the hat. OH GOSH, WHAT IS THIS SHOW?
"However, that doesn't mean I'll fall victim to their—ow in the head." It's not the line, it's the deadpan way it's delivered.
From that same episode: "LOOK AT HIS BOTTOM! ...HIS BOTTOM!"
And also: "Don't worry, it's no big deal; it was just a ball flying through a... head and window hitting face... it hurt."
And this: "It's a shame we're just now learning to speak... in English and stuff."
Then there's a part from the episode where they go to the fake beach. Tamaki slips on a banana peel and Vic starts doing this really weird noise as Tamaki slides across the floor on the peel, rolls for a bit, then slams face-first into a totem pole.
Yasuchika. Cockney accent. Aaron must've been waiting forever to have that chance...
You can tell, because you can hear him laughing quietly in between the lines.
When Aaron's supposed to be reading his lines about Honey in the Host Club, and instead of hearing Aaron even mess up you hear him laugh and go, "Yessss", because he was THAT excited about getting to rant about cake.
Nekozawa breaking into a Christopher Walken voice in the middle of one of his lines.
Hearing Caitlin Glass whining, "I can't do it! I don't wanna be cute! I wanna be a boy!"
Made funnier by Tamaki screaming his head off after this.
Haruhi: Today the pink one is...one of em and...I don't know which one the blue one is...I hate them.
From Episode 5:
Hikaru: We take our job very seriously boss. Kaoru: [making weird hand motions] Last night we... aaaaaaalohaaa.
Kaoru: I'm going to write the... ahh I'm gonna keep talking and... then I'm gonna do this next line. From... ah f*ck.
Haruhi: Maybe he's right. Maybe I... should learn... how to read.
From the same episode, "Guys, I'm really sorry... but I'm about to puke... all over you... BLAUGH! BLAAAAH!" The fact that Kaoru happily shouts "We forgive you!" immediately afterward makes it even better.
From the beginning of "The Refreshing Battle of Karuizawa!":
Hikaru: Kaoru, Brazilian wax isn't for women only.
"Could it be... VIC... MIGNOGNA?!"
From the ending of Episode 11:
Nekozawa: With this puppet's power, I... can... curse... [long choking noise] Rosebud...
Kyoya: Don't any of you care that Kasanoda went to see Haruhi who is changing clothes? I.e... disrobing? I.e. getting... nakee?Nuuude? In the buff? Au naturel? Posing for a pictuuure?Fine!
The Live-Action adaptation:
From the first episode, when Haruhi calls Tamaki "annoying", he's literally sent flying into the wall. The twins laugh it off, but Haruhi has an utterly baffled "Did that just happen?" reaction.
Every time Nekozawa appears and every time Tamaki overreacts to things.
Episode 8, specifically when Tamaki meets Haruhi's father. He's obviously not too happy with what he sees (Tamaki on top of Haruhi), but he quickly puts on a smile before flinging Tamaki against the window and helping Haruhi up. He then proceeds to mess with Tamaki by saying that he wants tea and then a nap before he demands an explanation from him.
Episode 9, in which Hikaru and Haruhi have their little date and the rest of the host club follow them around in disguise... Honey dresses in a pink dress and KYOYA of all people, wears a panda hat and poses as "her" boyfriend. And the first time we see them in disguise, they're sitting together, Kyoya patting/playing with Honey's hair. It seriously has to be seen to be believed.
As the credits roll in Episode 5, after Tamaki and Haruhi have that little heart-to-heart about the thunderstorm, the wardrobe and Haruhi's independence from others even when she needs help the host club start pondering how they never knew Tamaki was into S&M (after finding Tamaki putting ear muffs and a blindfold on Haruhi to help her stay calm through the storm) and proceed to whip out candles, chains, fake cat ears and such, and Honey even gets a blindfolded Mori on a chain leash and starts riding him around on all fours. (This is somehow funnier due to the fact that in this version Hunny is roughly Haruhi's height and the actors look to be similar ages, instead of being an Adorably Precocious Child.) And the wave of fanfics starts in 3, 2...
This version of Honey jump-hugs people crotch-first. Yes, really.
The episode where the boys try to train Nekozawa to be able to stand the light so he can reconcile with his sister. Kyoya's contribution? Opening and closing a pair of curtains with second-long intervals while Nekozawa Screams Like a Little Girl behind him. It's funnier than it sounds.
When his sister meets the Host Club for the first time, it goes pretty much the same as the anime...except when she points to the twins and asks "Twincest?" the boys are grinning ear to ear and nodding.
In the first episode, when Haruhi bought instant coffee ("commoner's coffee"), Tamaki shouts "I will drink this coffee!", followed by admiring gasps from the surrounding girls.
The first time Tamaki cries out "OKA-SAAN!!" Kyoya points at himself and goes, "You're talking to me?" with such a disbelieving voice...