!As this is a NightmareFuel page, spoilers ''will'' be left unmarked. Administrivia/YouHaveBeenWarned!

[[quoteright:300:[[WesternAnimation/TheUltimateEnemy https://static.tvtropes.org/pmwiki/pub/images/dark_danny_shadow.png]]]]
[[caption-width-right:300:"''Some things, my boy...are better left unsaid.''"]]
''Danny Phantom'' is a show about ghosts, so of course Danny and us will be bound to experience all kinds of nightmares.
* The whole notion that Danny may be faced with ColdBloodedTorture by his fanatical ghost hunter parents if they ever found out he was half ghost and the fact they voiced blatant hatred for Danny's ghost side originally and fairly frequently. Hearing one's mother and father say they plan on tearing you apart '''molecule by molecule''' is easy nightmare fuel.
* According to [[WordOfGod Butch Hartman]], Danny's transition into a Half-Ghost was simply good fortune. If Sam or Tucker had gone into the ghost portal like Danny, ''they would have been killed''.
* The "Masters of All Time" title card is possibly the most frightening with its portrayal of a feral, zombie-like Jack Fenton violently bursting from a clock and screaming murderously at the horrified Danny Phantom. While the episode itself does not have this actually happening, it definitely was a horror scenario just in one title sequence. Worse, all those hideous, pus-filled '''boils''' are everywhere, all over his body.
* "WesternAnimation/TheUltimateEnemy" has the creation of [[FutureMeScaresMe Dark Danny]], where he looms over his trembling human counterpart, before he murders his human self. It's not shown what Dark Danny ''did'' to Danny before blowing up Vlad's mansion, but given his status as TheUnfettered and Vlad's complete unwillingness to go into detail, it likely ''was not a pretty sight.''
-->''[[TakeOurWordForIt Some things, my boy...]]'' ''[[NothingIsScarier are better left unsaid.]]''
** And just before that, Danny's evil half claws Vlad's ghost form right out of him and then fuses with it. Dark Danny did some pretty disturbing stuff to his enemies.
** Dark Danny's creation. Vlad did not expect for the Phantom to violently react, especially not to rip it (though given what he said about ripping out emotions, one could be said that all the emotional turmoil was left in Phantom). Then Phantom overshadows Plasmius and ends up absorbing him. It's utter ''scream'' of anguish pretty much makes the event less of a FaceHeelTurn and more of a ''FaceMonsterTurn''.
** The BadFuture outright showing Danny's family and friends being outright '''killed''' in a fiery explosion in one of Clockwork's flashbacks.
** The fact that Dark Danny apparently destroyed the entire world and killed all its people outside of Amity Park.
** The entirety of Danny's RoguesGallery in the future, and all the awful stuff that was done to them. Johnny 13, the motorcycle junkie, is inexplicably in a wheelchair, Ember mentions her singing career going downhill when Dan essentially damaged her vocal chords with his ghostly wail, and the freaking Box Ghost is missing an eye and a hand, and he is [[TookALevelInBadass definitely no longer the incompetent comic relief villain as he know him to be]]. Not to mention Damon, Valerie's father, who somehow [[EyeScream lost an eye]] and '''one of his freaking arms.'''
** The worst one has got to be poor Johnny 13; [[NothingIsScarier we never find out what Dan did to him]], Danny doesn't seem to ''want'' to know what his future self did to him, and given how much more hostile he, Kitty and Shadow are towards Danny than the other villains (i.e, no jokes, no MotiveRant, nothin'), whatever Danny [[MoralEventHorizon did to him]] was [[ThisIsUnforgivable particularly horrifying]].
--->'''Johnny 13''': [[TranquilFury Been waitin' a LONG time for this, punk.]]
** Jazz realizes that the Danny she's been speaking to is not her brother. Dan keeps an eerily calm demeanor while Jazz begins to lose it.
--->'''Jazz:''' [[OhCrap You're not Danny!]]
--->'''Dark Danny:''' [[ThatManIsDead I was, but I grew out of it.]]
** Dark Danny turning around ''head first'' [[Film/TheExorcist Exorcist-style,]] accompanied by a horrible cracking noise as his neck does things it clearly was not meant to do. His chilling line while doing this really makes him all the more menacing.
---> '''Dark Danny:''' Nice try, Jazz. But me, my future, '''I'm inevitable.'''
** The scene where Dark Danny forces a Time Medallion inside Danny's body while the latter can do nothing but scream in pain.
** It’s extremely brief, but when told to name a second evil thing Danny has done, Clockwork shows the future, then concluding with a question that emphasizes his point. Just the sheer number he says illustrates the horrible things Dark Danny has done:
---> '''Clockwork:''' How about '''''two thousand'''''?
* [[Recap/DannyPhantomS2E17KindredSpirits "Kindred Spirits"]]. The darkest episode in the series after The Ultimate Enemy, naturally has tons of NightmareFuel as the above, if not more!
** Vlad planned to create a ''clone of Danny'' and then '''''kill off the original.''''' To make things worse, after Vlad's beloved stable clone was destroyed he had a huge FreakOut moment and was alarmingly close [[TranquilFury to murdering him ]] and likely would have if not for a timely intervention by Danny's friends. NightmareFuel doesn't even begin to describe it.
** "...And then ''[[DeadlyEuphemism you will be obsolete]]''."
** Also in that episode, when Vlad's clone son dies, Vlad himself faces Danielle with a terrifying face that screams pure violence and murder. Even after Danny first masters the Ghost Wail, [[UnstoppableRage Vlad got right back up again ready to rip them to shreds]].
** Vlad trying to force Danny to "go-ghost" through the machine. Danny's in ''obvious'' pain and keeps stopping mid-transformation and yet Vlad '''still''' tries to force it until the machine explodes.
* And then there's ''Identity Crisis'', the episode where Technus is accidentally released from the "Level 0" glitch. Danny attempts [[MesACrowd Form Duplication]] to fight him, resulting in nothing short of unadulterated BodyHorror (least of which being mouths for eyes and eyeballs on ends of tongues).
* Vlad's motivation for becoming a villain ([[MurderTheHypotenuse murder the protagonist's father]] so he can marry Maddie, his longtime crush and the protagonist's mother, and gain custody of her children and have the protagonist as his own son) is very, very, disturbing. This is repeatedly lampshaded in-series.
* The scene where Dani melts back into ectoplasm is both a TearJerker and nightmare fuel. Made even worse because it happens just ''after'' Danny does his last-ditch effort to save her.
* The scene at the end of "My Brother's Keeper" where Jazz uses the Fenton Peeler on Spectra. She literally '''removes layers of her youth''' until Spectra is an old lady. The fact that she gets older as her ''[[{{Squick}} skin is being peeled off]]'' is seriously disturbing.
** Spectra herself is very unnerving because of how [[RealismInducedHorror realistic her modus operandi is]]. Many teenagers have bad counselor experiences where [[UsefulNotes/VictimBlaming they are blamed for their own problems]] or otherwise given irrelevant advice that overlooks their actual issues, and there's no way of knowing if you're paired with a bad one until you're in there. Coupled with the fact that Casper High is full of the spirits of deceased teenagers, [[FridgeHorror imagine how much damage she had already inflicted before Danny dealt with her]].
* When Freakshow turns himself into a ghost with the Reality Gauntlet, he really goes all out on making himself look like a nightmare creature. %%Some context needed: what does he look like?
** Freakshow's first appearance in "Control Freaks" had a scene where he has a [[BrainwashedAndCrazy Brainwashed and Crazy]] Danny [[RedEyesTakeWarning with red eyes]] chase Sam onto a tightrope with a scythe, dressed up like the Grim Reaper. Danny's smile when he tries to kill Sam really doesn't help...
* The scene in which Poindexter first possessed Danny's body to be extremely disturbing, with the eerie green lighting, and Danny's contorting, spasmodic movements as Poindexter literally rips his spirit from his body.
* The scene in "Doctor's Disorders" in which Bertrand transforms is a major example of [[BodyHorror Body Horror]]: his skin glows green and begins to bubble as if it were boiling, while at the same time his head rotates gruesomely before his body expands and his scalp tears off, exposing his brain.
* Everything about Prince Aragon is very disturbing. He tries to kidnap a human teenager and force her to marry him, abused his sister for ''1600 years'', while keeping a dictatorship where not even time could flow properly for just as long, and on top of it all his transformation into dragon form is terrifying.
* Danny screaming and writhing in pain from the Blood Blossoms in "Infinite Realms." For a ghost, just being near the flowers is like being under the [[Franchise/HarryPotter Cruciatus Curse]]. And then Vlad shoves him into the circle so that he's surrounded by the stuff, making the pain ten times worse.
* Ladies and gentlemen, [[PhysicalGod Pariah Dark, the King of All Ghosts]]: he's said to be so powerful that the only way he was stopped was when a group of ancient powerful ghosts banded together, and even then they just knocked him out long enough to put him in a sarcophagus that kept him from waking up. It's also implied that when Danny was fighting him, the Ghost King was merely ''toying'' with him. Then there's Ember's line.
-->'''Ember''': He's only been free for a day and he's already destroyed our homes!
-->'''Danny''': And that's without the ring.
* Undergrowth. That is one freaky plant. With a horrendous bird-like beak, and a self-regenerating plant body, this guy's definitely not gonna give you a break when it comes to the creep factor. Add that with the fact that he brainwashed Sam and turned the entire city into a hellish wasteland with everyone being brainwashed and acting zombie-like. The tip of the iceberg? He is voiced by the legendary [[ComicBook/TheJoker Joker]] himself, Creator/MarkHamill.
* Nocturne, the cartoon hybrid between Freddy Krueger, with his regeneration and dream manipulation, and the Black Doom, with his ruthlessness and power hunger. Creepy voice, universe colored body, and those beady red eyes. Plus he harnesses the dreams of his victims through special helmets.
* In "Parental Bonding", [[https://images.app.goo.gl/vjTmxLPe48jp2zEc9 Sam's transformation into the dragon ghost]] is pretty creepy, with her skin turning blue and scaly, teeth becoming sharp, and opening her eyes to reveal her pupils are now [[RedEyesTakeWarning red slits]].
-->'''Sam:''' [[VocalDissonance SHALLOW LITTLE WITCH!]]
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