* The {{Animesque}} ImagineSpot.
-->'''Flower''': Horton's the greatest hero of them all! HAAAH!
** "[[EpicFail But Mount Nool is that way!]]"
** "I will make monkeys of these monkeys, for it is their destiny! HUUHHH?"
* Vlad choking on a bone and muttering to himself, "Holy moly!".
* The entire breakfast sequence, including Sally's motherly but offhanded "''That's'' one of my girls!"
** One that appeared often in the trailers; Ned tries to get a word out of Jojo...by using his interpretation of teen slang. Vow of silence or not, can you really blame [[OnlySaneMan Jojo]] for not wanting to dignify [[EpicFail that]] with a response?
** One of the daughters gets a test that's marked "A+++++".
** Another part of the breakfast sequence involves two of the daughters squabbling [[SiblingRivalry because one was using the other's hairbrush.]]
--->'''Hilda''': "Holly's been using my hairbrush!"
--->'''Holly''': "Hilda's been using ''my'' hairbrush!"
--->'''Mayor''': "Look! Over there!" ''(they turn, he swaps their hairbrushes)'' "There, all better." ''(they hug)''.
* The portraits of the various ancestors... including the "... not-so-great" grandfather.
* '''THE ANIMATION.''' Never before have CG characters squashed-and-stretched so much as in this film and the animators utilized it to great effect, eliminating any doubt that CG models can move just like hand-drawn characters!
* The business with the two Vlads- the bad Vlad... and the bunny Vlad that makes the cookies! [[note]] For context, Morton tells Horton that Sour Kangaroo has sent Vlad, but Horton says he knows two Vlads. [[/note]]
** [[SarcasmMode "Yeah, Horton. She's sending you a bunny with cookies."]]
*** Even if you don't like snark, this conversation after is funny.
---->'''Morton''': "I think we can assume it's the bad Vlad."
---->'''Horton''': "Good point."
** "Keep watching the SKIES (Morton pulls Horton's eyelids up, making his eyeballs bulge), Horton. Keep watching the skies..."
* When Horton first hears the speck and hears it yelp, he wonders if there's someone on it, or even a whole family. He then imagines a whole family of Whos clinging onto the speck and the youngest shouting "I WANT TO LIVE!".
* The scene in the Town Hall where the Mayor thinks that maybe they should cancel the Who-Centennial. The Councilman presses a smiley button, a dome descends around the Mayor and the council, and Muzak begins playing, causing the panicked Whos to relax. As this is happening, the Councilman is chasing the Mayor around the dome. In the next shot, he's strangling the Mayor. And then the next shot shows him pointing first to the Mayor and then to a picture of a donkey. [[GettingCrapPastTheRadar Probably not too hard to guess what the Councilman was calling the mayor.]]
* When the Mayor hears Horton's voice coming out of the drainpipe, he thinks it's his friend Bert playing a joke, which leads to him saying, "Oookay, Hor-ton - ''fake name'' - where are you?"
** He then calls Horton "Oh, voice from the drainpipe."
* The first time you see Ned the Mayor. He's stirring his coffee, then he bends to pick up his newspaper and spills it all without noticing. He then goes to take a sip and looks adorably confused as to where his coffee has gone.
** The deleted scenes show that the scene would have been extended. Ned finds his coffee landed into the wheelbarrow of a garden gnome, and tries to drink the coffee from out of it, getting him stares from his neighbor.
** An alternate opening seen on the DVD has Ned goofing around in the bathroom and proudly announcing that "The Mayor [[MundaneMadeAwesome will now brush his teeth]]!"
* "I don't even remember. Yes, I do. BLAAAARGH - you know, some guy was talking to me... ''not'' an elephant in the sky. A guy on the ground."
* Jojo's [[FunnyBackgroundEvent utter]] [[AudienceSurrogate confusion]] at the SuddenMusicalEnding, then eventually [[AsideGlance shrugging to the audience]] and joining in.
** The SuddenMusicalEnding itself.
** Horton's "that's a little high for me".
** Ned pointing out whenever a metaphor is used.
* When Ned discovers a snow day in the middle of summer, everyone else is having fun but he's afraid because one of the scientist's signs of impending doom she mentioned was "dramatic changes in the weather", which causes him to yell out "No! This is not fun! This is a sign of doom! Everyone stop having fun, immediately!"
* Anytime Katie is onscreen. Although it's honestly equal parts funny and equal parts... incredibly creepy.
** Katie puts her clover on her head, gets on her hind legs, and disappears backwards into the brush. It's both hilarious and, frankly, a little off-putting.
** It might be mean-spirited but Sour Kangaroo [[HypocriticalHumor kicking her across the jungle]], straight over a tree that resembles a field goal.
-->'''Tommy''': ''It's GOOD!''
** Katie's "beautiful in a really weird way" imaginary (probably) world, where everyone is a pony who eats rainbows and poops butterflies.
* When Horton yells "''THIS ENTIRE JUNGLE IS A '''HOUSE OF DEATH!'''''" upon searching for a place to put the speck and finding animals eating the plants.
* Entire Horton crossing the bridge scene.
-->'''Horton''': This looks kinda...precarious. Well, no need to worry. Obviously when they build a bridge like this, they'd taken into account that elephants will be crossing here.
** Later as he is halfway across the bridge with the ''bridge halfway gone''.
-->'''Horton''': I just need to think light. I'm light as a feather. I'm light as a feather!\\
(feather floats gracefully down on to bridge plank...then ''the plank gives way'')\\
'''Horton''': Heavy feather...
** While Horton is crossing the bridge, meanwhile the Mayor is visiting the dentist, already feeling a bit nervous. Every small earthquake that occurs (resulting in such things as dental rinsing water being poured into his ''eye'', and the Novocaine needle jabbing his ''arm'') the dentist is ''utterly nonchalant'' about it.
** In the following scene in the Mayor's house, Jojo plays the ComicallySerious to his father's antics, taking being told to put away anything breakable calmly but with a "What the?" look on his face.
--->'''Mayor''': "Stop looking at my arm."
* The Mayor glares at the Councilman's portrait.
-->'''Mayor''': He has the nerve to call me a boob? I would never call someone a boob. [[HypocriticalHumor HE'S the boob!]] Look at you. Yuck! Look at your face. And I bet you don't look so good ''with a STAPLER IN YOUR HEAD!'' [''throws a stapler at the portrait, which bounces off and hits him in the face, leaving a staple implanted on his forehead''] '''''YEEOWWWW!!!!!'''''
** His assistant Miss Yelp then removes the staple from his forehead ''barely even looking in his direction'' [[NoodleIncident like it's happened before]].
-->'''Mayor''': YAH! Thank you, Ms. Yelp.\\
'''Ms. Yelp''': You're welcome.
** Later during the Vlad chase, the Mayor rolls out onto his balcony, hits one of the railing pillars between his legs, then is shoved in further by his desk, a couch and a refrigerator... And just when things can't get any more painful, ''the stapler staples his forehead again'' and he screams.
** Later, Horton gets the chance to threateningly call the Chairman a boob, scaring him a bit before [[ItAmusedMe telling him he was just joking]]. You could tell from the Mayor's smile that he was quite satisfied.
* Vlad demonstrates to Sour Kangaroo on what he'll do with the clover.
-->'''Vlad''': Here's what I'll do to Horton's precious clover. I will take it, I will crush it, and I will ''devour it.'' (''swallows bone then starts choking; eventually pulls the bone out'') [[{{Squick}} Then I'll regurgitate it. Then I'm gonna devour it a second time]]. So, ''two times'' devoured!\\
'''Kangaroo''': Sounds...nice.
* The Mayor explaining who Horton is.
-->'''Mayor''': "Horton... is a giant elephant in the sky!" (quieter) "Don't bother looking, he's invisible."
* At the start Horton is teaching the class about leaf bugs with priceless results.
-->'''Horton''': There it is! One of the jungle's most amazing creatures: the leaf bug: In order to protect itself from predators, it disguise itself as a leaf. (''Horton touches the leaf bug. then starts fidgeting with it mumbling;'') This one's got quite a grip. C'mon, Lil Buddy, don't be shy. (''tries to pull the leaf bug off the branch; he loses his grip and falls flat on his head'') I guess I was mistaken, kids. (''Leafbugs swarm onto his body'') There are obviously no leaf bugs in this area. Even a--AH! THEY'RE ON ME! GET 'EM OFF! (''accidentally sucks one bug into his trunk'') I swallowed one! (''repeatedly slams his trunk to the ground, trying to get the bug out'') HELP ME! (''holds up his trunk to Tommy'') ''[[AC: Pull it out!]]''\\
'''Tommy''': (''look of disgust'') Uh, okay (''he and the other kids start yanking Horton's trunk'')
** Then when the bug finally falls out of Horton's trunk, Katie ''flicks her tongue at it and eats it.'' Then as Horton runs after the speck, Katie ''spits the bug out, scaring the other kids away''.
* One contact between Horton and the mayor
-->'''Horton''': Horton to Mayor! Come in Mayor! Over!
-->'''Mayor''' (''on his roof, holding a bunch of radios above him''): I get terrible reception here!
-->'''Horton''': '''''[[NoIndoorVoice HOW'S THIS THEN?! IF I GET UP REAL CLOSE, CAN YOU READ ME?!]]'''''
--->[''The Mayor is sent flying off the edge of his roof; he climbs back up again'']]''
-->'''Mayor''': Yep! Roger that!
* This conversation
--->'''Mayor''': "This is my wife Sally, my five daughters Hallie, Hayley, Helga, Hoolie, and Hannah, Ms Yelp, Dr Larue, Bert from Accounting, Mr Farfugen, and the old man in the bathtub"
--->'''Horton''': (recites all the other names) "And wasn't there an old guy in a shower?"
--->'''Mayor''': "Mm, bathtub".
* All the Mayor's 99 children wanting a bedtime drink. Then, he's seen carrying a lot of glasses of water.
--->'''Mayor''': "Lotta liquid, a LOT of liquid"
* This little bit of levity during [[TearJerker the saddest scene in the movie]].
--->'''Horton''': "Knock knock...that's where you'd say 'who's there?' if there were any [[{{Pun}} Whos there]]."
* When the Mayor ends up hanging from the chandelier.
-->'''Sally''': What are you doing?
-->'''Mayor''': What's it look like?
-->'''Sally''': Well, I'm no detective, Ned, but you are hanging from the chandelier.
-->'''Mayor''': I just thought it might look better somewhere it can't fall on us and crush us in our sleep. (''the chandelier falls with him on it, now hanging '' inches'' above the floor'')
** Later.
--->'''Mayor''': "Have you ever gotten the feeling you were being watched?"
--->'''Sally''': "Sure...I suppose."
--->'''Mayor''': "And have you ever gotten the feeling that maybe that thing watching you is, umm...a giant elephant?"