During the conversation between Neptune, Noire and Plutia when Neptune first goes to Planetune in the 80's, Neptune claims Noire has no friends. Both Noire and Plutia's reactions to this are priceless. Funnier is Neptune's reaction after she finds out Noire DOES have friends.
Anytime Iris Heart is on the screen. Anytime.
Special mention goes to her first scene, where she politely asks the villain present to wait while she torments her party members for a bit. After an... intense set of bargaining, she eventually thanks the villain for her patience. Said villain admits she just didn't want to have a yard of what was going on.
Pirachu called Arfoire "OBAHAN" and thus made her mad.
In English, the lines were more generic "old hag" insults that still spark her ire, but lack the same impact... until Pirachu tells Plutia Arfoire is only so cranky because she's menopausal.
This doubles as a Call-Back to the first game when IF made a comment about menopause when Arfoire first appeared.
Plutia questions why you don't have to travel through a dungeon in order to reach another nation in Neptune's world.
Neptune: Yeah, we retconned that.
Shortly thereafter, they comment that things would be so much easier if Noire built a road connecting the nations directly, only to hear Histoire yelling that they should do something about it... and then remember Histoire is nowhere near them right now. They were so lazy their own subconscious yelled at them to get something done. In unison.
Nep: (comparing Blanc and Plutia) And when it comes to HDD, yours is so much crazier.
When Noire, Neptune, and Blanc see Plutia holding baby IF, Compa, and Peashy, they all immediately assume she was pregnant during their absence and the children belong to her. Their overreactions are hilarious, right down to Neptune starting to recite the numerals of pi.
Nepgear gains the Emo Affinity! Neptune: The game system popped some kind of window up! Whats an "Emo Affinity"? Glad you asked. By worrying about her lack of personality, Nepgear acquired a "Learning Ability." Depending on the situation she finds herself in, she may learn various other unhelpful things. That is to say, these dont affect the game in any way. Neptune: Whoa, a self-aware tutorial window responded to me!
When Yellow Heart first appears, both Vert and Blanc agree to take her out, so Vert can have the largest chest among the CPUs again.
"I AM GOING TO LOWEE. THEY WILL HEAR ME COMPLAIN DIRECTLY. IN LOWEE."
In case you're wondering, Noire complains so much until Plutia gets fed up, transforms into Iris Heart and teaches her a lesson, resulting in breaking Noire. This continues even in the Basilicom, where Noire still sounds like a Broken Record, while Plutia is rather... satisfied.
After Neptune comes back from Leanbox and Nepgear is depressed because her sister left her behind, Neptune tries to make her feel better by saying she loves her. Also remember that IF and Peashy are still babies at this point.
Neptune: Nepgear! I, Neptune, your big sister... looooooves you! Nepgear: ...Huh? Plutia: Oh, my! Incestual confessions! (*Neptune and Nepgear continue to confess their love to each other*) IF: ...Dis is hawt. Peashy: Ooh, lovey-dovey sistahs.
While trying to make sense of Mr. Badd's 'daughters' and where they came from, Neptune comes to a conclusion. The fact that she says it with a >‿< expression on her face only makes it better:
Neptune: Nope, I got it! Youre a hermaphrodite! You sowed and reaped your own seed!
Early in the game, we get this gem after Noire says she'll be going into a big speech.
The thought of Anonydeath being surrounded by four Fake Noires is awkwardly funny with Noire being too uncomfortable about the situation.
The thought of having Multiple Iris Hearts running around due to Fake Purple Heart appearing. IF and Nepgear's response is being scared, while Blanc's response?
Blanc: The world would be doomed.
If you send ASCII out to scout and she returns without finding anything, she has this to say:
ASCII: I found jack squat.
Hyperdimension Neptunia Re;birth 3: V Generation
The new introduction scene, really just all of it. The massive rant Neptune goes on about Nepgear's tech hobby being introduced takes the cake.
The post-game scenario also uses this for all it's worth, with Neptune trying to remind Nepgear about the new intro scene and getting increasingly more detailed and more fourth wall breaking with each elaboration. The implication being that Nepgear forgot about it since the scene wasn't in the original Victory plot.
The introductory events for the DLC characters are all hilarious in their own way, but special mention goes to RED. At first Neptune assumes she was sucked into a white light like all the other Maker characters, but RED instead says she got there by jumping off a swing and jumping into a lake. Neptune immediately freaks out and begins questioning RED on what drove her to go so far; RED is understandably confused.
After the events where Hyperdimension Vert becomes an idol producer, Chika gets Vert to return home and get back to work by literally writing a ransom note that holds all of Vert's games as hostages. She can't get home fast enough!
Vert: (Reading Chika's letter) "My darling Vert, your nation needs you so stop messing around and get back to work! If you don't, your precious games will, one at a time-"
Nepgear, after taking suggestions from Vert to study on idols from anime and games, decides to watch one. Only it turns out to be the one with the mecha and not the other one because Neptune bought it awhile ago and Nepgear saw the word "Idol".