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* {{Anvilicious}}: In "My Fair Mandy", Grim questions why anyone would participate in beauty pageants (Mandy is only doing it to show up Mindy). Cue several moms encouraging their daughters to win for the sake of their love.
* BaseBreaker: Fred Fredburger became this after being extremely overused in CN's promos along with the excessive overuse of his [[TrademarkFavoriteFood nachos]] and [[ToiletHumor poopoo jokes]].
** As was Mandy, after she became a JerkSue in later seasons.
** Billy, between fans who find him hilarious and fans who find him annoying and one-note.
* BrokenBase: Over whether the show becoming increasingly DenserAndWackier was a good or bad thing.
* CrackPairing: Dean Toadblatt and a giant squid, canonically.
* CrossesTheLineTwice: [[ChristmasEpisode "Billy and Mandy Save Christmas".]] Features such things as a mall being burned to the ground as the MallSanta is mercilessly beaten (with The Grim Reaper implying that this happens all the time and Billy blaming it on the sad state of the economy), [[BadSanta evil vampire Santa]], Santa's evil vampire wife, and [[CrowningMomentOfFunny the local bully being eaten by a pack of flying vampire elves.]] Quite subversive compared to the average Christmas episodes, and even fellow childrens' cartoons that try to subvert the usual sweetness of a Christmas special don't take it that far.
** A lot of the humor can dip into this, it being BlackComedy.
* DarknessInducedAudienceApathy: With how grim and crapsack the world is and how unlikable Billy and Mandy can be to some, this can happen.
* DudeNotFunny: Some of Grim's misfortunes and suffering can fall under this.
* EarWorm: [[VillainSong BRAINS, BRAINS, I WON'T LIE. I'LL EAT THEIR BRAINS UNTIL THEY ZOMBIFY!]]
** The first end credits theme. "''Grim and Eeeeeeevil. Grim and Eeeeeeeevil.''"
* EnsembleDarkhorse: [[TheDitz Fred Fredburger]], [[VerbalTic yes!]]
** Jack O'Lantern has also gained himself a sizeable fanbase, [[OneSceneWonder despite only having appeared in a Halloween Special.]] [[PopularityPower This is possibly the reason he was included in the video game.]]
** Dracula.
** Skarr, the only mainstay from "Evil Con Carne".
** Admiral Wolverine Lightningbolt.
** [[GreekChorus Sir]] [[MetaGuy Raven]].
** [[{{Music/Voltaire}} The evil brain-eating meteor]].
** [[EvilIsSexy Eris]], the goddess of chaos.
** Hoss Delgado. He was popular enough that he ''nearly'' starred in the spinoff-series-turned-TV-Movie, ''Underfist''.
* EvilIsSexy: Eris. Never mind the gap in her teeth.
* FamilyUnfriendlyAesop[=/=]SpoofAesop: Billy learns from his inner frat boy that, just because someone is different from you, you shouldn't be afraid of them. You should be '''angry''' at them!
* FountainOfMemes: Probably one of the most quotable Cartoon Network shows ever, especially in the earlier seasons.
* GeniusBonus: The episode where Billy meets mushroom-growing dwarfs has a scene where he escapes from Yogi and Boo-boo by hiding in a cave. Brown bears really are afraid of caves.
** The show is filled to the brim with horror movie references, most of which are fairly obscure even to adult fans.
** Mandy quotes Creator/AleisterCrowley in one of her typical (very) cold openings: "To do what thou wilt shall be the whole of the law".
* GrowingTheBeard: Generally agreed to be around the time this show split off from ''Grim & Evil''.
* HilariousInHindsight: In one episode, Grim is seen watching a Franchise/MyLittlePony parody called "My Troubled Pony" and enjoying it very much, in spite of the fact that he's a male adult and he's clearly not within the show's demographic. [[WesternAnimation/MyLittlePonyFriendshipIsMagic Fast forward to 2010...]]
** Nergal is a [[NoodlePeople tall and thin]] HumanoidAbomination with CombatTentacles and wearing a [[BadassInANiceSuit suit]]. Now [[Franchise/TheSlenderManMythos who does that sound like]]?
** In the beginning of ''Big Boogey Adventure'', Billy doodles "cops fighting dinosaurs" instead of writing out plans, and then remarks that "they should be working together" when Irwin calls him out. [[Webcomic/AxeCop It wouldn't be the last time that concept came up.]]
** An in-series example: in the beginning of ''Billy & Mandy's Jacked-Up Halloween'', Irwin's first Halloween costume is Sleeping Beauty, as a lame attempt to get Mandy to kiss him. Fast forward to ''Big Boogey Adventure'', and it's '''Mandy''' who's now the sleeping beauty that needs to be awakened with a kiss. And guess who kisses her?
* JerkSue: Mandy, DependingOnTheWriter.
* LauncherOfAThousandShips: Mandy, if you can believe it. She's been shipped with Billy, Grim, Irwin, Nergal Jr., [[FoeYay Mindy]]... Hell, [[CrackPairing even]] ''[[WesternAnimation/InvaderZim Dib]]''!
* MagnificentBitch: Whenever Mandy brings her A-game. One particular is when turned herself into a slug and tricking TheResistance into believing her [[WeaksauceWeakness weakness]] are frogs.
* MemeticBadass: Hoss Delgado.
* MemeticMutation: See OverlyLongGag on the main page.
** [[{{Music/Voltaire}} Well hello little boy! Don't be shy! Step right up, I'm a reasonable guy! Don't be frightened by the look in my eye, I'm just your average evil meteor from outta the sky!]]
** Judge? Where are the nachos?
*** Yes!
*** I can spell my name real good! F-R-E-D! F-R-E-D! B-U-R... G! E-R! [[TheDitz Fred Fredburger]], yes!
** YOU DON'T TELL DRACULA WHAT TO DO! DRACULA WAS BORN KNOWIN' WHAT TO DO!
*** Vampires don't suck! They scrape! And lick! Scrape! And lick!
** Pretty much EVERYTHING that Sir Raven says...
*** "Do not cry for him. DO NOT CRY!"
*** "YOU FOOLS! YOU'VE MESSED WITH THE NATURAL ORDERRRRRRRRRR!"
*** "IMPORTANT! COMMERCIAL! MESSAAAAAAAGE!"
*** "'''THEEEE!''' '''''EEEEEEEEEENNNNNNDDDDD!'''''
** Grim was the original brony.
** Grim's Peanut Song from Episode 2: "Look at me, I'm a kitty cat! I wear a bowl of peanuts for a hat. If I eat them all, I will get fat! Blah blah blah I'm a kitty cat!"
** LIKE AN ANGRY WOMAN.
** Lord Byron is Billy's [[JoJosBizarreAdventure Stand]]!
* MoralEventHorizon: Quite a few, though they're offset only by the show's NegativeContinuity (usually).
** Grim and Mandy have had a number of potential moments, usually involving leaving Billy to a CoolAndUnusualPunishment.
** Billy, though a good kid, has tried to kill his "adopted" son just because he's afraid of spiders.
** Irwin has allowed a Pyramid to be built in his honor, regardless of whether or not everybody remains brainwashed.
** Nergal forces a number of people, including the viewer, into transforming into his "[[WasOnceAMan Friends]]" in the second episode he appears in.
** Boogey crossed it in ''Wrath of the Spider Queen.'' During the contest for who would become the future Grim Reaper, Velma was close to winning, but Boogey decided to rig the voting. When Velma finds out, [[spoiler: she thinks Grim tried to cheat]], costing him his only friend.
** [[SadistTeacher Ms. Butterbean]] crosses it in ''Substitute Creature'' when she ignored Sperg bullying Junior because he bribed her with an apple. To really [[KickTheDog twist the knife]], she tells Junior that it's okay for Sperg to do it because he was bigger. You don't feel bad when Junior glues her to the ceiling and takes her form.
* MostAnnoyingSound: DESTROY US ALLLLLLL!!! DESTROY US ALLLLLL!!!
** To a lesser extent, any time Billy laughs.
* NauseaFuel: Several times in the show.
** Many of the injuries, such as when Pud'n [[EyeScream gets an eye full of cactus and pulls it off, revealing a hideous, skinless red eye]].
** Or Billy's nose popping.
** Or when the closing iris closes on Billy's head and a bunch of blood and snot sprays from his nose and his eye pops out.
** Or when Billy and Mandy force Grim to resurrect the school mascot cats. That, in itself, is pretty bad, but when Billy asks one of the cats to scratch his back...his skin and muscle get shredded by the splintered claws of the undead cat, and his spinal column pokes out.
** In the episode, "Zip Your Fly," Mandy accidentally swapped her head with that of a fly after messing with Grim's zipper. That's pretty standard for the show, but then after losing the zipper to the dump, she ends up eating ''the entire landfill'' before she can find it and get her body back.
* TheProblemWithLicensedGames: Averted. The video game based on the series is a surprisingly fun beat-em-up style fighter with plenty of characters from the show, all voiced by their actual voice actors, with Music/WeirdAlYankovic as the announcer!
* TheScrappy: Billy is this to more than a few viewers, due to how arguably flat he is as a character and for being a often pointless ToiletHumor dispenser. He's even this in universe.
** Fred Fredburger is also this in universe, ''[[EveryoneHasStandards even managing to annoy]]'' '''Billy''' ''with his stupidity''. Among viewers, though, he's a BaseBreaker, with many who love him and many who feel he ended up over-used. (Although he wasn't half as over-used as characters like [[WesternAnimation/FostersHomeForImaginaryFriends Cheese and Goo]].)
** Mindy is one of the most annoying {{Alpha Bitch}}es ever created.
** Mandy for some. Due to her JerkSue status being too exaggerated by many. It's to the point where she can give [[Series/DrakeAndJosh Megan]] a run for her money.
* SeasonalRot: The final season is considered pretty crappy, though Underfist is well-regarded.
** The second or third season after being split from ''WesternAnimation/EvilConCarne''; by then, its AdoredByTheNetwork status made it considerably less enjoyable.
* SpotlightStealingSquad: Irwin in later episodes.
* TearJerker: In "Son of Nergal", Junior attempts to fix his teddy bear, Mr. Bonkers, after Mandy rips its head off.
-->'''Junior''': It's *sniff* going to be okay. I'll put you back together and *sniff* you'll be my friend and I'll be your best friend...
** Billy saying goodbye to his pet chupacabra Daisy.
** The flashback in ''Wrath of the Spider Queen.''
* ToyShip: Admit it- you've all considered this for Billy and Mandy at least ''once''.
** Or Irwin and Mandy.
** [[HoYay Or Billy and Irwin]].
** Or Junior and Mandy, to a lesser extent than the other two.
* VillainSue: Mandy, already being a JerkSue in her own series, graduated to this in the Crossover with the KND. Verging on becoming a full on BlackHoleSue.
* WhatDoYouMeanItsForKids: Like nearly all of Creator/CartoonNetwork's in-house programming (specifically those from the "Cartoon-Cartoon" era of shows), this show is a kids' cartoon on the outside, and on the inside, is packed with a lot of things that most normal channels wouldn't allow to touch children's animated shows. In the case of this show, it's BlackComedy, some mild sex and toilet humor, and disturbing imagery that makes ''WesternAnimation/InvaderZim'' look like ''My Little Pony''.
* WhatTheHellCastingAgency?: Creator/GilbertGottfried as ''SantaClaus''.
* TheWoobie: Pud'n and Jeff. Also, Skarr. He is just trying to move into the neighborhood, trying to avoid his previous life as TheDragon[=/=]TheStarscream.
** Billy, at times.
** JerkassWoobie: Grim has his moments too.

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