Disgaea 4: A Promise Unforgotten is the fourth game in the Turn-Based Strategy series Disgaea by Nippon Ichi. The game revolves around Valvatorez—a vampire who forbade himself from drinking human blood after he made a promise 400 years ago—and his campaign of reformation against the corrupt government of the Netherworld. With him is Fenrich, his loyal demon wolf servant, and Fuka Kazamatsuri, a deceased middle-school student who was sent to the Netherworld and should have been turned into a Prinny, but because of budget cutbacks just had a Prinny hat slapped on her instead.Other characters include Vulcanus, the Angel of Avarice; Emizel, the son of the Netherworld President; and Desco, a monster girl whose ambition is to become the Final Boss. Axel returns as the warden of Hades and Valvatorez' boss.Features include true high-resolution sprites (with the option of switching to the traditional low-res sprites), new Magichange commands and the ability to use a pirate ship to invade and plunder other players' games.An Updated Re-release for the Vita with the title Disgaea 4: A Promise Revisited (Makai Senki Disgaea 4 Return in Japan) has been announced. In addition to including all of the Downloadable Content from the original game, it will also contain a new bonus story.
Aliens Are Bastards: A group of 20 billion planets all consider humans to be such pests they want to kill us all. The fact this will destroy the netherworld and Celestia doesn't bother them, they actually seem to consider them being wiped out killing two birds with one stone.
Angrish: Fenrich breaks into it when Fuka suggests that he might not hate her with the passion of a thousand fiery suns.
Fenrich:Argh! Must you keep-!?... Ugh, what an ill-natured damsel.
The Vita remake is slated to have a third story showing how Valvatorez met Artina. It also includes Fuka and Desco Time Travelling, and introduces a new character named Nagi Clockwork.
Anti-Frustration Feature: In the previous installments, if you tried to capture an enemy you weren't able to create yet, your entire Base Panel along with anyone inside, would be killed for the duration of the battle. (Or in the case of Item World, till you returned to the hub or miraculously found a Mystery Room Hospital) In D4's Item World, if you tried the same thing and proceeded to the next stage anyway, everyone in your Base Panel is miraculously revived as if you never made the attempt at all.
Apocalypse Maiden: Subverted with Artina. She wasn't destined to be the cause of the world being screwed up, but pretty much became the cause of it anyway as the result of her death.
Arson, Murder, and Jaywalking: The heroes are shocked to discover a newspaper falsely reporting Emizel's death, glossing over their rebellion, and misspelling the word "Prinny". Well, at least Val thinks the misspelling is a serious offense.
Asskicking Equals Authority: Essentially how the president remains in office. He stays president until he is defeated, at which point the position is open to the victor or whoever the victor chooses. It eventually goes to Axel, since Valvatorez didn't care and was more concerned about Nemo. And then Torn Desco came in...
Bait and Switch: The introduction to the game has Valvatorez describing fresh, dripping juices... only he's talking about sardines. Similarly, the animated OP for the game shows Val lunging at a woman, only for the image to change to him happily munching on sardines.
Batman Can Breathe in Space: Lampshaded. When Valvatorez and his crew arrives on the moon, Fuka notices she can breathe normally. Fenrich remarks that demons don't need oxygen and the reason on why she can do it is because she is dead. Which raises a relevant point when you meet Judge Nemo there.
Big Damn Heroes: What good is praying when all hope is lost? Flonne: It's...LOVE! Praying will become the Power Of Love!
Bi the Way: A Succubus made with the "Bewitching" Personality voice set will proclaim this in one of her Cam-Pain-HQ lines.
Bloody Murder: "Delusion", one of the succubus' magichange attacks, has her strip in front of the party member that was wielding her, resulting in a massive Nosebleed that damages, if not outright kills enemies in front of said party member.
Bolivian Army Ending: The God Ending ends with the party facing off against eight million minor gods sent by the big guy himself. So far, they've killed eight hundred thousand of them.note "Eight million gods" is a Shinto reference.
Bonus Boss: In the postgame, you can fight and recruit Axel, Flonne, Raspberyl, Etna, Laharl, Asagi and Zetta. Prinny Kurtis can be fought and recruited as well, if you encounter him enough times in the Item World then pass a bill in the Senate. Pringer X and its other versions also serve as bonus bosses, except they can't be recruited. Finally, there's a bunch of DLC characters you can fight and recruit.
The Bro Code: Mentioned by Fuka when she briefly considers pursuing Valvatorez.
Fuka: Aww, but Artina and Fenfen might get up in my face. Plus, stealing you from them would be breaking the friendship rule.
Bullet Time: Used hilariously in HD Asagi's Dead Battle skill, which places her in a shootout with the targeted enemies.
Butt Monkey: Axel! You thought he had it bad in the second game, you ain't seen nothing yet...
Artina says 'he's was born under a hopeless star'.
Call Back: Both Fallen Angel and Archangel Flonne have an attack that summons a dragon.note A Dragon Zombie for Fallen Angel Flonne and a normal Dragon for Archangel Flonne While she never had this as an attack in the previous games, she once summoned a dragon to aid her in her boss battle in Disgaea: Hour of Darkness. She even uses the same incantation — Durian Dragon Dranyago.
In the Fuka & Desco show, if you talk to Laharl in the Cam-Pain HQ, he will sometimes bring up Prinny reincarnation only to immediately wave it off. Anyone who played the first game will know why.
Call Forward: In Tyrant Valvatorez Mode, Fenrich makes a comment that Valvatorez would probably put his all into any job, even the lowly job of a Prinny Instructor.
The Cameo: Before being released as DLC, Pink from Dark Hero Days Axel Mode makes a few brief silent appearances throughout the game and appears as an enemy in some battles with Axel. During Axel's Love Dynamite S, during the normal ending credits, and during the Axel ending credits though infected by the A Virus. If Axel is in a cutscene, Pink will be hiding somewhere. She also makes occasional random appearances in Item World Innocent Towns.
The Tera Star spell drops the solar system on the targets.
Getting The Fish Strong! ship leads the Prinnies to tearing up the moon, much to Fenrich's annoyance.
Comically Missing the Point: When Fuka tries to rob the Netherworld mint with Desco and an unwilling Artina in the Fuka & Desco Show, the three of them are stopped by Flonne, who insists they're about to commit a terrible crime: how can they even think of robbing the Netherworld mint without first coming up with an awesome Phantom Thief team name!?
Comic Trio: Fuka (the leader), Desco (the fool) and Vulcanus/Artina (the Only Sane Man) have this arrangement in the Fuka & Desco Show.
Convection Schmonvection: The area that serves as your home base in Hades is completely surrounded by flowing lava. It could be argued that demons would not be affected by this in the same way humans are, but then again, fire spells do plenty of damage to them...
Crapsack World: Things have really gone downhill in the Disgaea universe since the last game. Hades is overflowing with sinful human souls, the Netherworld hierarchy is incompetent, bloated and ineffectual, Celestia is near-bankrupt because human Faith is in decline, the Netherworld itself is on the verge of collapse from a critical lack of Fear Energy from the Human World, the Human World has been consumed by pollution and vice, and in the end God Himself gets tired of all this shit and decides to forsake creation itself.
Dare to Be Badass: Valvatorez gives one such speech to Emizel after he's disowned by President Hugo.
Valvatorez: Haven't you realized that your existence can easily be erased without your identity? Why don't you leave your father's protection, stand up for your own free will, and take a step forward with your own two feet? It's the only way you'll ever be able to prove you exist.
Dead All Along: Judge Nemo's been dead since the beginning of the game. That's the reason on why he can travel freely between the Netherworld and the Human World.
Also Fuka, though she's the only one who hasn't realized it.
Declaration of Protection: Along with his oath to not drink blood until he shows Artina true fear, Valvatorez also promised he'd protect her for as long as that took. Unfortunately, he didn't take promises then as seriously as he does now, and Artina was killed three days later. It was the last promise he's ever broken.
Description Cut: When the team learns Vulcanus is still on collection duty in the Netherbattle Tournament, the angel has to reassure them that the money isn't going to be wasted this time around. After all, what's Flonne going to do? Spend it on another giant robot? Cut to Flonne planning on exactly that.
Did You Just Flip Off Cthulhu?: Valvatorez effectively gives God himself the middle finger at the end of the game. In the God Ending, however, he manages to piss off God a little too well, and God declares total war against him, which he starts by annihilating both Earth and the Netherworld.
The Vita port adds a new scene in which Val is transported to another dimension to speak with God, who wanted to see the one who defeated Fear the Great and warns him not to defy him. Val, however, tells him to stop acting high and mighty and meddle with everyone again, otherwise, he will come back and give God a beating. So, Val essentially and directly gives God the middle finger!
Did You Just Punch Out Cthulhu?: Val gives one to God that sends him back to the Hades Party, promising to give him more should God ever mess with the world again.
Valvatorez: Grit those teeth, God!!!! And learn what itís like to feel pain!!!!
Episode 7. Always outnumbered, flooded with Reapers that hit hard and eat your SP, and crippling geo symbols everywhere.
Then you go to the X Dimension of Episode 7. Ouch. To make matters worse, you need to capture one of Reapers to obtain a part needed for the Land of Carnage.
One could make the argument that Episode 8 is even worse. Same problems as Ep. 7, outnumbered, crippling geo symbols, but also Geo Puzzles and enemies with long ranges. And at the end, you have to fight the boss once, and then a giant version of her a second time without the opportunity to heal up in between.
Divine Intervention: God gets fed up with Earth enough to decide that Rocks Fall, Everyone Dies and activate Fear the Great. In the God Ending, once Valvatorez manages to stop that, God sends an aspect of himself to deal with the party personally.
Aspect of God: God has concluded that you cannot be stopped merely with Fear the Great alone. Thus, he has dispatched me to confront you.
Downloadable Characters: For the North American release, Fallen Angel Flonne can be obtained by preordering from either NISA store or Gamestop. Aside from her, you have Adell, Rozalin, HD Asagi (Free in the U.S. and Europe), Overlord Priere, Mao, Kyoko, Asuka, Pink, Main Hero B, Pleinair, Prism Red, Gig, Pram, Petta, Nisa, Marona, Ash, Hugo, Des X, Nemo, KingKrichevskoy,note Though visually, it's Mid Boss with Krichevskoy's antenna hair, a Badass Cape, and a fabulous new outfit and Pirohiko. Some of these characters also come with classes from the previous games like the Deathsabers, the Celestial Hosts, and the Kunoichi. Finally, two new classes — a Medic class (Designed by Noizi Ito) and a Necromancer class (Designed by Kohaku Kuroboshi) — have been added.
Downloadable Modes: There are two downloadable scenarios similar to the Disgaea 3's Raspberyl Mode. The first takes place before the main game and features Valvatorez during his days as a Tyrant — which includes an alternate version of Valvatorez (Tyrant Valvatorez, similar to Fallen Angel Flonne). The second focuses on Fuka, Desco, and Prinny reincarnation. In addition, there's added gameplay modes like Tournament Mode and Survival Mode.
Extra: With each character release, there will downloadable ship parts for your pirate ship and stage maps for both the map creator and the hub.
The Dev Team Thinks of Everything: Using the map editor, you can assign any character in your party to act as any NPC in your base... And they all have different things to say depending on what they're assigned to.
When you switch over to the Fuka and Desco Show, characters in the Cam-Pain HQ have different things to say. It replaces the sardines line with candy, they acknowledge that it's the Fuka Party now, and the DLC characters have different things to say depending on the chapter.
Don't You Dare Pity Me!: When Artina willingly offers Valvatorez her blood so he won't have to feed on other people, Valvatorez responds that he refuses to drink the blood of a woman who doesn't fear demons and swears to her that he'll show her true terror before he touches blood again.
Vulcanus/Artina offering to let Val finally drink her blood in the Vulcanus epilogue seems quite a bit like she's offering something else. The illustration that follows◊ doesn't help.
During the post-game, after hearing Axel's poem, everyone cheered for him. Among those cheering was a Prinny who says he grew a third peg leg.
Almost all of Gig's dialogue with Priere in the Netherbattle tournament.
Downer Ending: If you finish the second-to-last level (Boiling Point) as Val solo with him at Lvl.500, the game ends with God, enraged by the party's actions, destroys both Earth and the Netherworld and subjects the party to a Fate Worse than Death.
Everybody Lives: After every boss battle in the game, and even most normal battles, the enemies you just fought seem to stick around for a while to argue with the heroes over one plot-advancing point or another before running off or poofing themselves away, regardless of how badly you destroyed them in the last battle. In fact, the only character who ends up even remotely dead is Judge Nemo, and even he is coming back as a Prinny. Or, after clearing the third chapter of the Fuka and Desco Show, you can get him back in human form, but with the power of Fear the Great but without the darker colors, and he acts like rude.
Everyone Is Bi: The game allows you to set up any two units as "lovers", sex or species be damned. And of course there's this line:
And so, everyone admitted that they don't mind a little trap action, even among plant life. That's... good to know!
Evil Cannot Comprehend Good: Almost literally. Angels are invisible to humans who have no faith, which is why Nemo cannot see or hear either Vulcanus or Flonne.
Exact Words: In Artina's ending, she tells Valvatorez that he has fulfilled his promise to bring her to despair - by making her despair over his safety.
Failure-to-Save Murder: To Judge Nemo, Valvatorez is just as responsible for Artina's death as the people who killed her both because he failed to live up to his promise to protect her and because he didn't punish her killers.
Fartillery: The Dragon's Break Wind attack is a flaming variant, while the Orc uses the (somewhat) more standard variety with its Orc Hero Gas attack.
Feelies: The US Premium Edition comes with a artbook, a OST, and a Fuka figurine. The Super Premium comes with all that and an additional 9 figurines.
Sixth Ranger: Axel, well sort of. He isn't recruitable until Post-Game, but he's heavily featured in the animated opening and acts as a Neutral NPC to the group at times during the main story. Pretty much fully takes on this role in the Post-Game scenes however.
Flanderisation: Axel suffers from this greatly. In Disgaea 2: Cursed Memories he was an idiotic dork but the game makes it clear that his raging ego and showmanship is part of his act as the "Dark Hero" and at heart he's a decent guy who cares about his family and doesn't like to commit real evil. In Disgaea 4, his egotism and idiocy are ramped up to dangerous levels, to the point where he threatens the entire Netherworld and doesn't realise it. To be fair, Axel does state that he was playing the part of the Warden the entire time (and there is evidence to prove that) and he acted like that to save Pink who needed help when they jumped Netherworlds together.
The treatment of Prinnies in general. In Disgaea: Hour of Darkness, although it is made clear that Prinnies are treated worse in the Netherworld than in Celestia, Etna's comical levels of abuse (low pay, physical abuse, using Prinnies as impromptu chairs) are still treated as a exceptionally bad example and Running Gag. In Disgaea 4, Etna's behaviour comes off as downright nice in comparison to the new norm, where the minimum wage is one sardine for a twenty-three hour work day.
Foregone Conclusion: In Vita port's Time Loop episodes, Fuka and Desco discuss this when they learn they've been transported to the war 400 years ago in which Tyrant Valvatorez and Sister Artina met, knowing that Artina will eventually die.
Foreshadowing: In one of the bad endings. Lose to Vulcanus, and at the very end, you can see Flonne and a not-so-shadowed Great Flongor X.
Forever War: Parodied in one of the bad endings: after everyone in the Netherworld is transformed into Axel by the A-Virus, all of the Axels wage war against each other over who is the best looking. Since Axel refuses to believe anyone's better than him, this means all the Axels keep fighting the Battle of Axfools indefinitely.
Fusion Dance: Monsters can fuse into one another in the middle of battle to create giant versions of themselves, or with human-type characters to become weapons. It's a option in the Senate for Monster Foreign senators, which raises their voice level. Oddly enough, they can do it with more than one monster.
Gameplay and Story Segregation: A usual for Disgaea, but the Adell cutscenes are a doozy. It doesn't matter if you have 10 billion HL or have everyone in the party stronger than Val, your funds are 'limited' and Val is the 'strongest.'
The fight with Zetta will end with him calling Valvatorez the strongest, only for Val to say that he needed the rest of the party to help, and therefore Zetta is still the strongest individual. He says this even if he is way tougher, and won the fight solo.
One of the most blatant examples is that Val refuses to drink blood in story but has absolutely no problem with using his in-game HP-draining abilities against human or monster enemies.
One of the Evil Symbols allows you to have your party members participate in assemblies. However, they can vote "Nay" just like other senators, and should your vote be denied, will fight against you if you decide to persuade them by force. This can lead to situations that could never happen in a million years in the story, like Fenrich fighting against Valvatorez.
Global Currency Exception : The Map Editor shop which require CP to purchase items rather than HL, which is used everywhere else.
Gondor Calls for Aid: Genjiro manages to supply Flonzor X with the awe energy it needs to stop the moon's Colony Drop by broadcasting Valvatorez's efforts to save the world on every TV screen on Earth, while Hugo similarly mobilizes the Information Bureau to gather it from demons.
The "incomprehensive Ninja"' personality types yells out in a foreign accent Japanese words like "sushi" and "harakiri" that are hilariously inappropriate for the situation. Bonus points for not knowing Japanese and speaking fluent Engrish when not blurting random Japanese words. The "incomprehensive Ninja" is probably someone who idolizes "Glorious Japan" so much, he/she has decided to insert a few Japanese buzzwords in a desperate attempt to sound cool.
Val (In the English dub) will often talk about Japanese for sardines during On the Next. Even Axel pipes in at one point.
The orange Prism Ranger is the incomprehensive ninja, Up to Eleven!
Heroic BSOD: Desco undergoes a very literal system freeze upon learning that Fuka wants to be reincarnated in the Fuka & Desco Show.
Heroic Will Power: Valvatorez went from Tyrant-level Supreme Overlord to level 1 through abstinence for 400 years. He wanted to keep a promise to someonenote Artina and he didn't want to die because that would technically break the promise.
Hide Your Gays/ Suspiciously Specific Denial: A Heavy Knight with the "Overwhelming" voice set has a Cam-Pain line that has him noting that he sees beauty in men's muscles, but is quick to cite rather nervously that it isn't a sexual thing.
Hoist by His Own Petard: Axel unleashed Desco to make her fight Valvatorez's party... then got fried by her lasers.
Homoerotic Subtext: The game has absolutely no qualms with pointing out that Fenrich's obsessive loyalty to Valvatorez is more than a little suggestive. Fuka considers it as canon as Val/Artina.
And it's taken even further in the DLC scenario "Tyrant Valvatorez Days". Upon seeing Tyrant Valvatorez in action, he starts to wonder wheter he is "the man who will makes his dreams come true".
Given the fact that (As mentioned) other charcters notice it (Including the canon love interest, Artina) and the fact that the game pokes fun it at it (Like Androids mentioning Val/Fen Slash fics upon creation) one has to wonder if it isn't just text at this point.
All the problems in the Netherworld can be traced back to how humans inflict harm and suffering upon themselves for profit and power, and thus they stop fearing demons and start fearing themselves, thus redirecting the fear energy, a vital essence to the netherworld, to themselves.
Also, due to the same reason, humans lost most of their faith, which is vital to Celestia in the same way the fear energy is to the Netherworld.
Humans seem to held to a double standard compared to demons. Most of the things that are considered wrong for humans to do and are treated as dark events are treated as comedic when demons do them. While Valvatorez doesn't approve of it, demons appear to able to get away with anything.
Flonne's Great Flonzor X. Some of the ships that become available through DLC such as Laharl's Laharl Kaiser V and Mao's Getter Mao also count.
Fuka's final skill, which summons Pringer X.
Hunter Of Their Own Kind: The Prinny Extermination Squad, which is made up of human souls who are supposed to become prinnies, but couldn't due to lack of materials.
I Did What I Had to Do: President Hugo is well aware of how far the Netherworld has fallen and that he made such horrible decisions. However, because of the lack of fear energy, it was either he let the Netherworld crumble or give in to Judge Nemo to preserve the Netherworld as much as possible. Either way would have doomed the Netherworld.
Karma Houdini: The guard who kills Artina walks off with absolutely no repercussions.
Keep the Reward: In the Netherbattle Tournament DLC, Valvatorez bluntly refuses Krichevskoy's reward of his Netherworld, and even scolds Krichevskoy for trying to pass his responsibilities to it for someone else.
Kill the Cutie: Deconstructed to hell with Artina's death (pre-story line) as it is the root cause of everything that has gone wrong during the course of the game's story line. See No Good Deed Goes Unpunished.
Lawyer-Friendly Cameo: The Spell Keepers for the Omega spells include Anime Tenchou (Fire), Holo (Wind), Lotte (Ice), Bikkuriman (Star) and Index (Heal). An interview with NI President revealed that they're all good friends. 
Level Editor: Maps can be created, then uploaded for other players to play, rate, and comment on. By playing user-made maps, points can be earned that allow for the purchase of more map parts, textures, backgrounds, and geo effects.
In addition to this, the hub area is now highly customizable. Any cleared map can be used as a hub (Including your created maps), and any of your characters can run the various shops and services, or simply idle for the purpose of providing conversation. Unfortunately, Sony required this be dialed back in the US and Europe — maps can still be created, but only via pre-designed map blocks — raw customization is impossible, and all mooks in said maps will have random names. Presumably this is to prevent obscene maps, although that other game by Sony had a highly customizable map editor without this requirement... As an unfortunate side effect, this means that the wealth of Japanese maps will be unusable in the US and EU versions, and the US and EU versions may be incompatible with the Japanese version for the "Item World Invasion" multiplayer.
Level Grinding: As with all of the games in the series, it has this in spades. However, the new Magichange features ease the grind a great deal, by allowing you to level one human character and four monsters at once.
The Professor character class. She's even got a personality type called "Mad Scientist". Let her work on your base as a nurse and she becomes a Mad Doctor, gleefully treating her patients as the test subjects she's been asking for on the Cam-Pain map.
Genjuro, Fuka's dad. It's his job title. He created Desco and DES X just because his daughter wanted a little sister.
The Bone Dragon, Dragon, Wood Golem, and Rifle Demon classes all possess a low movement range and low speed aptitude, but compensate for it with high HP and/or defense, and high attack. However, since both movement range and aptitudes can be boosted to an extreme degree (Either by equipment or using the Char World), it's entirely possible to turn one of them (Or any other class, for that matter) into a Lightning Bruiser.
Mooks: A staple of the series, generic units are split between humanoid (Warrior, Archer, Android, etc) and monster (Dragon, Orc, etc). Monsters use a generic weapon (claws / teeth / etc) and can't throw, but can magichange. Some of the unique characters look humanoid but are technically monsters (Like Raspberyl). All the generic Mooks have alternate personalities (voice packs) that you can choose between, allowing for at least some variety when using multiple versions of the same mook — or seeing enemy mooks. There's also an unlockable shop that sells Palette Swaps of every character, allowing them to be more visually distinctive as well.
Moral Dissonance: The game is extremely Avilicious about wrong doings that humans do toward eachother, but anything done by demons do to themselves is treated as okay because demons are Laughably Evil. So basically humans are held up to a double standard.
My Dad Can Beat Up Your Dad: During the Netherbattle Tournament, both Laharl and Mao talk about how badass and powerful their fathers were. The only thing keeping them from completely fulfilling the trope is that their respect for their fathers is begrudging at best and when Emizel points out that they do care about their fathers, they completely deny it.
Adell's second attack has him use parts of the Disgaea 2 versions of the Tiger Charge, King of Beasts, and Rising Dragon fist skills in a combo.
Both Flonne's first Special Skill is a reference to the first game. See Call Back above.
A few of the alternate colors for the DLC characters resemble their alternate forms or other characters from their respective games. For example, one of Gig's alternate colors makes him resemble Revya's in-game sprite while one of Rozalin's alternate colors turns her into the true Zenon.
A few of the DLC character's evilities try to mimic the mechanics of their original games. Prier's "Extra Turn" is based on the "Re-Action" mechanic in La Pucelle Ragnarok, Marona's "Confine" is based on her ability to summon phantoms in Phantom Brave, Gig's "Best Buds" is based on the Squad leader bonuses in Soul Nomad, etc.
Necessarily Evil: Demons are viewed this way. Their act of inflicting fear in humans is done so that humans learn respect and preserve order. In exchange, the Fear Energy that's produced keeps the Netherworld alive. It is also beneficial toward angels as the actions of demons cause humans to look to the heavens for guidance. In exchange, it grants angels with Awe Energy which gives them power and courage.
Never Trust a Trailer: Axel is featured heavily in the game's opening, taking center stage with the playable protagonists. While he's a recurring villain and even temporarily "joins" the party at one point, he's not actually playable until the post-game.
Old Save Bonus: Nippon Ichi has stated that one's old Disgaea 3 saved game will unlock an Evil Symbol that allows party members to enter the senate to vote on bills. Said Evil Symbol can also be unlocked through normal gameplay at some point, so those who don't have Disgaea 3 aren't missing out.
Punished for Sympathy: The entire plot of Disgaea 4: A Promise Unforgotten is more or less driven by the fact that the Big Bad Nemo was once a human who was injured in a war and helped by an enemy nurse called Artina, who was executed as a traitor for it (and ended up convincing Valvatorez to give up blood, allowing Nemo to take over his position). Thus leading to his Start of Darkness (and her becoming the angel Vulcanus).
Ragtag Bunch of Misfits: We have a sardine-loving vampire who is very serious about keeping promises, his serious and cunning werewolf servant, a middle schooler who just can't accept the fact that she's dead, a cute Final Boss-in-training, a former coward who wishes to grow stronger, and a money-grubbing angel (And that's not even including the secret characters). Even Hugo lampshades it before the fight with him.
Red Oni, Blue Oni: Valvatorez and Fenrich respectively. This is despite their opposing color schemes and the general stereotypes of their species in fiction.
Robot Girl: The Android (which should be Gynoid...) class, which seems to take inspiration from Bubblegum Crisis. The male version — "Battle Suits" — is decidedly less sleek and fanservicey.
Rube Goldberg Device: One of the Prinnies' magichange attacks is to set off one of these that throws a giant bomb at the enemy.
Whenever Axel appears, he usually calls out Valvatorez off screen. The screen would then pan over to Axel to which Valvatorez responds "Warden Axel!" The gag is later subverted when the screen pans over to a random Gunner with the same voice, an A-Virus victim.
Fuka's constant denial that she is dead.
Also, the fact that there are four consecutive episodes labeled "Final Episode" before the main story actually ends.
Each On the Next segment quickly devolves into Valvatorez sharing "interesting" facts about sardines with the player.
Sequel Hook: Given that it's Disgaea, it might not amount to anything, but even in the post-game the main characters are still worried about God going after them. There's also all those aliens...
A new scene, in which Valvatorez directly calls out God adds to the above.
Ship Sinking: Despite an exchange implying that there will be some sort of relationship between Valvatorez and Fuka, nothing comes out of it and Fuka ends up supporting Val X Artina. On top of that, while she does consider it, she decides not to pursue Valvatorez in her own epilogue since she knows she'll have to deal with Fenrich and Artina.
Talking Is a Free Action: Sometimes the main characters go off on a tangent while the enemy demons patiently wait for them to stop talking so they can attack. It's as if the cutscenes were just as turn-based as the gameplay. Occasionally this is lampshaded.
Take That: Possibly at the length of Disgaea 3's main game, as the seventh episode is called the final episode in the title card and Disgaea 3 was only eight episodes long. Disgaea 4 is actually ten episodes long.
True Final Boss: This is how Des X is described, although in the game she's only the final boss of Chapter 8 and the Fuka and Desco DLC Scenario. But there actually is a real True Final Boss: Four avatars of God. They appear as giant Eringas.
Unexpected Character: Most of the characters that have made it into the game as DLC have been highly demanded via polls, are main characters of previous NIS games, or are used as a "gateway" for the downloadable classes. Then there's King Krichevskoy who was never playable in his own game or any game afterwards. Yes, Mid Boss is King Krichevskoy who has beenplayablebefore, but this is first time players get to use the magnificent demon Overlord who sealed away Baal.
Unwilling Roboticisation: If you create an Android, a random valkyrie will be captured and forcefully transformed into an Android.
Upgrade vs. Prototype Fight: A non-mechanical example happens with the biological weapons Desco and Des-X. Although the latter is supposed to be more advanced of the two, they actually have near identical stats and skills. The former actually gains her ultimate skill while the latter doesn't, making up for it by having extra range on the two skills she shares with the former.
In the Japanese script, Desco loves to use the word "desu" at the end of her sentences, to the point of it being abnormal. Made more amusing by the fact that it's written in a way that can be romanized as "death". In Japanese, it even puns off the way her name is spelled in katakana - "Desuko" - which could be read as "desu girl"... or "death girl".
There's quite a few of them amongst the various monster classes, like the Nekomata's "nya", the Orc's "buhi", and the Wood Golem's "gogo", though in some cases, the tic is exclusive to a certain personality for the class. As with the former, most of them are only present in the Japanese dub.
Don't forget the Prinnies, dood!
The Cat Sabers and the Deathsabers spice their dialogue with cat noises. Even the big boss of the mint uses them.
Withholding the Cure: A non-villainous example: Vulcanus kept the cure for the A-Virus (Angels' blood) secret until it became apparent that there was really no other option but to use it, because angels are strictly forbidden from wounding themselves.
The Worf Effect: Although Emizel says that they're all powerful, every major demon that shows up in episode 7 suffers from this including the President himself. Somewhat justified as most of the demons have become much weaker due to the lack of Fear Energy. Some of said demons return in the postlude, much stronger than before. Lampshaded by Fuka, who points out that all these supposedly super-powerful foes Emizel keeeps dressing up don't actually seem all that powerful.
You Make Me Sic: At least two. Raspberyl's Magichange weapon switched from a sword to a staff, but the Imperial Cross skill favor text still calls it a sword skill. Also, Laharl's map is called: 'From Anether World!' That last one might be a pun, though.
Done hilariously. The A-Virus works over a period of time, leading to much angst over inevitable doom. Said virus turns them into a clone of Axel. The symptoms include blonde hair, Hot Blood, and slight (or increased) stupidity.
Creating a zombie leads to a world-wide version of this.
The Necromancer class can turn people into zombies by either killing them, or using her special skill. (Which only looks if she can One-Hit Kill the enemy.) She does this to her herself when she dies. She only has 1 HP, but keeps the level and SP, so she can still fight. As a enemy though...