The intro sequence, which is pretty much an Establishing Character Moment in the entire series. Etna decides that since Laharl won't wake up, she's gonna have to resort to shooting him. He wakes up and asks about the weapons behind her, and Etna defends he's a heavy sleeper. When she tells Laharl that his father died two years ago while he was asleep, he grows angry and asks why she didn't wake him earlier, to which Etna responds "what do you think I've been doing all this time?"
Stage 6-3 for instance:
Enemy Prinnies: We challenge you to a game of baseball, dood!
In "War of the Netherworld, part 2", everytime someone mentions that Jennifer is about to be modified, Laharl, Etna, and Flonne all imagine a giant robot version of Jennifer stomping around a city until Gordon yells at them for it.
In Episode 3 of Afternoon's Etna Mode, Flonne confronts Etna at the Sea of Gehenna...wearing a sentai mask. Calling herself 'Justice Flonne', she swears to defeat Etna, and after being chased off the first time, she comes back, claiming to have powered up. All she does is turn on lights where the mask's eyes are.
Etna: That's it? So your eyes are glowing...?
Flonne: Yes. Now, I can see in the dark.
Etna: Anyone who walks around at night, wearing that mask has gotta be some kind of crazy.
In Episode 9, when Jennifer and Thursday meet the Disgaea trio. This is Thursday's response when he senses lifeforms approaching:
Thursday: LIFE FORMS ARE APPROACHING. OH $*&% RUN RUN RUN...!
And in his first scene:
Thursday: GORDON KEEPS STARING AT JENNIFER'S THIGHS. PERVERT - PERVERT - PERVERT!
Vulcanus' reaction to the contents of a book he finds while sneaking around Laharl's castle;
Vulcanus: This page! This page! All of these pages!
Captain Gordon, Defender of Earth!'sgloriouse introduction.
And his Bad Bad Acting when he wants to sneak away from Laharl. "LA LA LAAAA!".
Even funnier: if you have a good enough Thief, you can steal the Horse Wiener from the zombie and equip it yourself!
Laharl and Flonne meeting Jeniffer, and hearing assumptions that demons are horrible monsters with tentacles, which the two of them take offense to and wonder where she got those ideas from.
After the boss fight with the previous Defender of the Earth, Flonne is angry at Laharl for not throwing the fight and says he's "The worst" before the ghost cuts her off and says that even though he lost he can still pass on. Everyone prepares to move on, but Laharl and Etna start to wonder what exactly Flonne was going to call Laharl. Thurday promptly states "Now calculating, now calculating," and as he prepares to give the answer, Flonne does a Big NO and slams him into a wall. Enta replies she's worse than a demon.
Upon catching up with Mid-Boss, Gordon, Jennifer, and Thursday do a hammy Power Rangers-esque pose. Flonase gets jealous that they're stealing the show and forces Laharl and Etna to go along, and their presentation is so damn unenthusiastic.