Marco: (laying on his back, hands behind his head) "O mighty Helmacron dead guy, we grovel like a video game addict trapped in an arcade without a quarter, that's how much we grovel. You would not believe the depths of our grovelry! We grovel like a guy with a large order of fries and the only saltshaker is at the table of the school bully."
Also, Marco discovering that the completely out of their gourd Helmacrons are all female.
Marco: Oh man, now I'm really scared. It's an entire race of Rachels
Marco driving Cassie's dad's pickup, managing to hit every trashcan.
Jake: Do you hate trash cans? Is that it? Do you just HATE TRASH CANS?
Jake: Get off the sidewalk, you lunatic!
And that time he stole an Abrams tank, threatened some guy with it, and flattened Chapman's house (he needed parking space, dammit!) Let's face it, Marco Drives Like Crazy.
"Anybody gotta pee? Go now, cause I'm not stopping at every Stuckey's we pass."
Visser One decides to invade Hollywood, which she concludes is obviously the most important city in the U.S., because of how often it's mentioned in broadcast media.
"Alive. My mother was alive. I saw Rachel giving me the fish eye from across the room. I mouthed that one word: alive. Evidently Rachel doesn't read lips. She misunderstood what I'd said and responded by mouthing two words I won't repeat."
"Self-destruct sequence activated. T-minus-15 minutes to self-destruct. Thank you and have a nice day!"
And then Visser Three turns purple. Why? Because the Animorphs told him grape juice would get out the smell.
Before that, she got Jake's dog, Homer. Poor mutt, unlike wild animals (and humans) didn't know better.
"This, Cassie, is the ancient art of whittling."
Ax's description of one driver's reaction to Marco's driving:
"I saw a pick-up truck, with its horn blaring and its driver forming a sort of salute with one raised finger."
Ax pulls out plenty of these later on in the series.
The men on "The Young and the Restless" do not wear shirts. I am young. And I am occasionally restless.
"Ax?" "Yes, Marco?" "Put on a shirt."
I would like to shuffle my artificial hooves to the music with you. But you cannot have my body. My bod. Dee. My bo. Dee.
I believe the smell is causing me to become deranged. I may have to run away in panic.
"You do not know me," he said, "but I am a juvenile delinquent. I do not trust authority figures, I probably will not graduate from high school, and statistics say my present rowdiness and vandalism will likely lead to more serious crimes. I am a dangerous fellow, and I am causing mayhem in this store." He reached behind her and pulled three jars of baby food from the top shelf. Shoved them behind a box of macaroni. Shuffled the Cheez Whiz in front of the Marshmallow Fluff. Tossed a bag of lady's shavers onto a bag of hamburger buns. "There. I have now shamelessly destroyed the symmetry of this shelf, undoing hours of labor by underpaid store employees. If you could see me, you would be frightened."
Ax got off to a good start during book 5, when Jake and Marco took him to the mall and he discovered taste. Aste. Tuh-aste.
From that same scene:
Jake: We're on schedule. So far, so good. Marco: Jake, can you do me a favor? Can you not say that? Any time one of us says "so far, so good", something goes wrong. Ax: Suh. So far so good. So far so good-duh. So fuh-far so guh-good. Good-duh. Marco: Oh, man.
Ax's first experience with chili: "THIS IS A WONDERFUL FOOD!"
From #27, The Exposed: The Chee can only be reactivated from the Pemalite ship, which is at the bottom of the ocean. Suddenly, the conversation takes a turn for the Seifeldian:
Cassie: I thought that show was called Voyage to the Bottom of the Sea. Marco: No, that was the one where Captain Nemo fought the giant squid. Rachel: Who won?
There's also when Ax informs the kids that the secret alien technology hidden at Area 51Zone 91 is an Andalite toilet.
A primitiveAndalite toilet. They've made significant advancements since it crashed.
When Marco, Cassie and Rachel are questioned by a soldier at Zone 91, and asked for their parents' phone numbers:
Rachel: "We have to get out of here. Fast! I gave him the phone number for Pizza Hut delivery."
Marco: "I gave him the number for the Sports Scoreboard recording."
Cassie: "I just gave him one-two-three-four-five-six-seven-eight!"
Marco: "Eight? You gave him eight numbers? Remind me not to ever be a spy with you."
The Animorphs are trying to work out why the Yeerks would be interested in a meatpacking plant.
Cassie: "Contaminate the food supply? Kill a lot of people?"
Ax: Nonsense, if the Yeerks wanted to kill a lot of humans they could simply use their dracon beams to ignite the atmosphere.
Marco: Well. There's a happy thought.
In "The Sickness", Marco passes the time while helping to carry an extremely sick Jake back home by listing all the ways to say 'throwing up'. It is funnier than it sounds.
Later on, after all the characters have gotten over the titular alien sickness, they talk about what they did while sick. After the rest of them complain about being too sick to get out of bed, throwing up all the time, having an alien inside their head, and such, Tobias reminds them that, since he's always in the form of a hawk, and that Cassie's father, a vet, tried to stick a pill up-
Tobias is funny in general in that one. When he first gets sick, after being the only one besides Cassie not to, Cassie's forced to put him in a cage until her dad can treat him, next to an Eagle, which his hawk instincts aren't so happy with. We can tell he's not amused, the whole thing is hilarious.
In The Andalite Chronicles: The mental image of Elfangor driving across the Taxxon homeworld full-speed in a YELLOW MUSTANG while DRINKING DR. PEPPER THROUGH HIS HOOF and LISTENING TO THE ROLLING STONES may well be one of the funniest things in science fiction.
Not to mention Ax eating popcorn (including it's container) and concluding it tastes quite a bit like cigarette butts.
The revelation that Jake and Marco once spent several hours arguing over whether cheese tastes yellow or green.
In #16, where the Animorphs are trying to hide in fly morph in a bathroom. While asking where everyone is, Tobias describes a very smooth surface with a pool of water below. We barely discern that it's a toilet. Then, it suddenly gets dark.
Marco: Caution: Falling objects.
In #10, Marco manages to write three pages of a term paper before coming up with a topic. "A topic will... emerge. I just have to keep writing until I come up with a topic." Jake's suggestion is "The use of rhetoric to obscure a lack of content." Made even better later on in the same book, when Marco mentions offhand that he got a B on his paper.
The distraction in #16. They burst out of a supply closet, and Rachel (in grizzly bear morph) proceeds to...mop the floor, while Jake (in tiger morph) carries the bucket for her.
A lot of the messed up blended morphs from that book have funny names. At one point, a ticked-off Jake refers to a half trout, half gorilla morph as "morphing into surf and turf." At another, Marco decides that a half-spider, half-skunk morph is either a skider or a spunk.
When the future Visser One first finds Earth, she begins investigating by picking up some of the numerous transmissions zipping around the planet... and absolutely panics when she picks up an episode of Star Trek, not realizing that it's a TV show and thinking that humans were a lot more advanced than we actually are.
The group takes Ax (in human morph) to see a Star Trek movie. Ax is very confused by the experience, claiming that the Enterprise is a stupid-looking spaceship ("I know what a real spaceship looks like!") and stating that Klingons are actually females of some species he has seen before. And then he gets distracted by the numerous "globules" (candies) littering the theater floor.
In The Separation, Erek, a member of a secret ancient, alien, pacifist android race with extremely advanced holographic technology and the appearance of large, metal bipedal dogs, who have preserved the essence of their extinct creators in domesticated dogs and participated in human society for thousands of years in secret, claims that the animorphs are simply too weird for him.
From that same book, the fact that Marco PHYSICALLY CANNOT STOP making jokes about the fact that there are two Rachels hanging around, even though one of the Rachels is very violent and has already nearly killed him for it once. It's a lot of joke, cringe, joke, hide, joke, etc.
The whole scene where Ax, Marco and Tobias attempt to acquire duck DNA.
An example that details the Two of Your Earth Minutes trope quite humorously (although this instance concerns distance rather than time):
Ax: "...fifteen of your miles."
Marco: "You don't have to say 'your miles'. They are everybody's miles."
Ax: "What about the countries that use kilometers? See? I am learning!"
Also the fact that Ax, who often comes off as overly serious when he's not in human morph, is obviously quite deliberately keeping various running gags going. The 'Don't call me Prince/ yes, Prince Jake" one, as well as this one:
Ax: ...and we have seventeen minutes left in morph.
Marco: (after a pause) Seventeen *minutes*?
Ax: (correcting himself) Seventeen of your Earth minutes.
"Entertainment Tonight! We've got stars, alright! We'll entertain you and drain you of all of your thoughts tonight!"
Cue Jake smacking him in the back of the head with a pillow.
Marco pretending to be Cassie via e-mail in book 16.
Even better, Jake catching on and playing along.
Ax avoiding detection by Cassie's dad: "I am from Canada. I am Canadese."
"I see. And does a tornado have feet?"
From book 12, The Reaction, in which Jeremy Jason Mccole, a teen heartthrob actor intends to endorse The Sharing. At first, the boys' reaction is, "It's not as if he's Michael Jordan or Wayne Gretzky," until...
Cassie: It would be as if...the entire female cast of Baywatch endorsed something.
Marco (in a hushed, horrified tone): He has Baywatch-level power?
In book 20, The Discovery, Marco has to speak to a human who isn't in on The Masquerade, while in morph. His way of going about it?
Greetings, Earthling! Klaatu barada nikto! I come in peace!
Earthling! Your son ditched school early!
Book 21, in which the Animorphs infiltrate a secure location by morphing fleas and riding on Jake, morphed to dragonfly.
Cassie: Did anyone ever read the Miss Spider books? This could be Miss Spider Goes Flying.
Book 22, a mostly serious story, in which the side plot is that the Animorphs stop a summit meeting being targeted by the Yeerks—which they accomplish by morphing elephants and rhinos and destroying the hotel complex.
I guess if you think about it, hanging out with a bunch of politicians talking about peace must be kind of dull. After a few days of that, maybe you kind of welcome massive, enraged animals barging through your living room.