President Hime learning just who the "handsome masked cat" really is in the second story of Episode 8 in The Animation. Aika's English VA delivers a hilarious Reveal line when she asks him what he's doing in that strange getup in the dub.
Any time Aika is startled and screams loud enough to send the birds scattering. It happens twice within minutes in one episode of The Natural.
President Aria went into an Alternate Universe of Aria. Everyone is genderswapped but retained their original voice actors, even the guys. One might find it funny with the genderswapped Akatsuki and Woody.
When Cait Sith stamps Akari and President Aria's foreheads.
From the manga: When Akari meets Woody she rides with him on his sky bike to help him make deliveries. At the end of the chapter, Aika is talking with her about the "Disgraceful Undine who was flashing her panties on a sky bike." Fast-forward a few chapters when Woody tries to explain to Akatsuki how he and Akari met when she yells out, "Woody-san, that's top secret!" followed by a tiny text of, "My panties..."
From that same chapter, Alice's Not So Above It All moment when she's waiting outside of the cabin, sees Akino approaching, and yells out an excited, "Grandma!" Cue Luminescent Blush as everyone who inside poked their heads out to see the commotion.
In that same chapter, Aika teases Alice about Athena actually hating cats and that she'll secretly off Maa with a knife when Alice isn't looking. Later, Athena tells Alice, "We need to talk about that cat you're hiding in your wardrobe," while holding a knifenote for making dinner. Cue Oh, Crap! from Alice before grabbing Maa and running the hell away!
"Akari-chan, I hate to break this to you, but you're rowing backwards." Akari's face, especially in the anime, is priceless.
The very first episode has Ai introduced as a Deadpan Snarker so her initial exchanges with Akari and some Snark-to-Snark Combat with Aika before she warms up to both of them bring in some great laughs.
In the manga version of the story where the main trio first meets Grandma, Alice has a great Surrounded by Idiots moment as Aika tells Akari to not be so hyper around Grandma, Akari says that she may not be able to, and Alice asks herself out loud, "Why do I hang out with these two?"
During the final episode of The Animation when Ai spills the beans to everyone on just what Akari was saying about them in her emails.
The entire fourth Picture Drama story where the competition between the three main Undine companies is depicted as an all-out war, culminating with Alicia getting Aika to defect to Aria Company simply by asking.