The series opens as Angel Trainee Flonne descends into the Netherworld in front of a burning castle in the middle of a lake of lava, having been sent to assassinate the Overlord. Skip to two years later, she still hasn't found him, and heads into what she believes is a tomb to take shelter. Here, she falls through the floor and discovers herself in a garbage heap — why it's there is never explained, but she forgets all about it after spotting a coffin with the Overlord's crest on it. Hoping she may have found her target at last, she cracks it open, only to be disappointed that it contains a young demon, not her target. Introducing himself as Prince Laharl, he is startled to discover his current resting place and that it's been two years since he went for a nap. After some... misunderstandings, he is reunited with his father's former vassal Etna and her personal squad of Prinnies. Accompanied by Flonne, who doesn't think she can go back seeing as how her target actually choked to death shortly before she arrived in the Netherworld in the first place and wants to see if demons are truly as evil as they claim to be, the trio (and the Prinnies) set out for the Overlord's Castle, seeking to place Laharl back on the throne that is rightfully his.Hilarity Ensues.After finally getting the throne back, a new problem pops up when a giant space fleet arrives from Earth's dimension, seeking to lay waste to the Netherworld and conquer it. Laharl, not one to put up with this sort of thing, puts an end to their plans and discovers they were manipulated into it by Vulcanus, of Celestia. Hijacking their flagship for added insult to injury, he pilots it off to Celestia to show them what he thinks of this.
Death as Comedy — King Krichevskoy, at least at first. Laharl reads in a newspaper that his father died choking on his afternoon snack, in brightly-lit office, in the middle of the day. Laharl has an Imagine Spot of the scene, and laughs.
Double Entendre — Etna has a blatantly innuendo-filled conversation (that we only hear the final part of) with Flonne in about the 4th episode. In fact, Etna does this a lot.
Dub Name Change — Inverted. The boar demons Hoggmeiser and Porkmeister are referred to as Zenisky and Koganesky, which are their names in the original Japanese version of the game.
Groin Attack — In the below-mentioned conversation Etna has with Flonne after they start travelling together, she mentions that she gave an unidentified nosy guy a very firm kick in the "you know where" (Flonne doesn't know where, though).
This conversation actually happens at the start of the 5th chapter in the games as well.
Getting Crap Past the Radar — Maharl's take on how her parents met. She basically all but tells us that her mom was a prostitute that Kirchevskoy used to hire after his wife died, to the extent that Etna freaks out and tells her to stop, as she's heard more than enough.
Goldfish Poop Gang — The Defenders of Earth get turned into this after the second episode.
Hammer Space — Laharl stores his (rather large) sword inside his scarf.
Captain Gordon's idea of a hero. Just listen to anything he ever says.
Laharl is also hammy. Looks like he has RitaRepulsa's voice and laughter. Like mother like son!
Laughably Evil — Laharl, since this is a comedy anime. Also, Vulcanus in Episode 3.
Lethal Chef — Flonne tries cooking for the group in the episode that loosely homages the Prinny World location. Laharl takes a few bite and is sick... although, given Laharl is a Card-Carrying Villain who gets freaked out by people just talking about love, peace and joy, and the fact he sprouts a thought bubble in which he is running playfully through a field of flowers and laughing with joy, it could be just that Flonne's food is so chockful of her positive attitudes it's unpalatable to him. But, then again, Flonne states she's never actually cooked before/isn't a very good cook when Laharl demands she make him something to eat.
Etna also tries it after Laharal states how bad it is and and also turns blue in the face. It is likely genuinely that bad. Also, Laharl orders Etna to cook something at this point, but she claims her cooking would be worse.
Made of Iron — Laharl. He was poisoned, and instead of dying (like anyone else in the world would have), he slept it off for two years. He can also hold onto Flonne's pendant, which would burn most demons rather badly, but Laharl takes it like a champ.
Mythology Gag — This series could really be considered more of an Alternate Continuity that happens to reference lots of elements from the original game. For example, Maderas calls up a pack of busty (if chastely dressed) succubi and catgirls who start chanting positive phrases like "eternal love", which makes Laharl so freaked out he can barely fight. This is a loose adaption of a background effect from an actual fight in the game, which has the effect of cutting Laharal's attack stats by 50%.
Perverse Puppet — It turns out Maharl is actually a puppet in the shape of a demon vaguely like a female Laharl. The "doll" she carries everywhere is actually the real demon animating her and using her as a cover. Though this doesn't stop her getting up and walking around on her own in one scene in one of the last episodes.
Pretty in Mink — Maharl wears a fur trimmed coat, in a matter just to make her look cuter.
Road Cone — The ending is a mix of the game's Good and Normal endings: Laharl spares Seraph Lamington's life, declaring it's what Flonne would have wanted, then uses up his life force to resurrect Flonne as a Fallen Angel, only to reincarnate as a Prinny.
Also, you'll notice that Laharl manages to turn himself back to normal just before the end credits. Another small divergence.
Running Gag — Flonne gets most of them. She tends to fall flat on her face rather often, and her cooking is not very good. There's also Vyers, who gets depressed over eventually referring to himself as Mid-Boss... on two separate occasions.
Shamu Fu: Replaces the daggers and bombs as the Prinnies' weapons.
Stupid Sacrifice: There doesn't seem to be any reasons as to why Kurtis had jump off the spaceship while holding the bomb, killing himself in the process, instead of just tossing it overboard, except because he's supposed to die in the original game.
Tentacle Rope: Thursday when programmed to do evil grabs Etna and Flonne.
This Is Unforgivable: Often played for laughs, like in Episode 2 when Vyers says this to the protagonists for nicknaming him Mid-boss just like in Disgaea 1 and in Episode 3 when Vulcanus says this upon seeing Flonne's change in personality while she's sleeping with Laharl and Etna and attempts to kill her only to fall right into a clam instead.
The only time this trope is played seriously is in the finale when Etna says this to Seraph Lamington for the punishment he gave Flonne for killing some of her fellow angels. Then again, anime are really good with this trope.
Too Dumb to Live — The Prinnies. They're not too bright in general, but it becomes most obvious when they attempt to establish their own home, Prinny World, on a small floating island... which begins to sink after too many Prinnies show up. They also didn't notice that the loud-mouthed, almost-naked kid with a giant Prinny hat and no Verbal Tic actually wasn't a Prinny.
Trailers Always Lie — The two promotional trailers for the anime seemed to stay closer to the source material and even hinted that there would be a battle between Laharl and Baal. None of that appeared in the anime.
At the end of each episode, Etna breaks the fourth wall to make up elaborate and dramatic claims about what the next episode will be (Much as she did in the game). They're pretty much all lies, though some slivers of truth do get through on occasion. Sometimes, the other characters get involved as well, replying to Etna's claims.