Ghost villains Amorpho Amorpho (voiced by Danny Mann) is a ghost able to change his appearance into that of any human or animal at will. More mischievous than malevolent, he desires attention and pursues it by morphing into someone else's appearance, to play pranks that leave the corresponding person to take the consequences, for what he actually had done.
Bertrand Bertrand (voiced by
Jim Ward) is a small, amorphous blob-like ghost who can transform into various monstrous creatures. It serves Spectra and helps her enact her plans. He is incompetent in his attempts to scare people and is barely taken seriously by either the heroes or the other ghosts. In an alternate future depicted in "The Ultimate Enemy", he is married to the Lunch Lady Ghost and has a daughter with her (Box Lunch). Dark Danny is a cruel, malicious ghost who cares little for anything other than himself, causing as much destruction as he sees fit. Dark Danny came to be after an explosion of the Nasty Burger restaurant killed Danny Fenton's family, friends, and teacher. Overcome with grief and guilt, Danny moved in with Vlad Masters, feeling that only he could understand his pain. Danny asked Vlad to remove his emotions. Honoring his wishes, Vlad separated Danny's human half from his ghost self; later, Danny retaliated, doing the same to Vlad. The ghost-half of Danny then attempted to possess Vlad, eventually fusing their bodies together. Plasmius's ghost-half overwhelmed Danny's, creating an even more evil and more powerful version of the two halves. He spent the next ten years destroying the world. Through time travel, the present-day Danny defeats Dark Danny and imprisons him in a Fenton Thermos which he gives to Clockwork.
Fright Knight The
Fright Knight (voiced by
Michael Dorn) is the representative of
Halloween. He is a powerful, gruff knight who spreads terror from his winged horse, Nightmare. Fright Knight's sword, the Soul Shredder, is able to send others into their worst nightmare via contact.
Ghost Writer The
Ghost Writer (voiced by
Will Arnett) is an author who resides in the Ghost Zone. He can create anything by typing on his keyboard with the added effect of forcing everyone to speak in rhymes, which continues even after the keyboard is destroyed.
Hotep-Ra Hotep-Ra (voiced by
S. Scott Bullock) is the mummy-like spirit of an ancient minion of King Duulamun, an Egyptian pharaoh who resembles Tucker Foley. He was released from his eternal sleep when Tucker looked into the mirror at the front of Ra's sarcophagus. He served Tucker and helped him regain his kingdom as pharaoh, but secretly planned to take over the kingdom once it was restored. Deceitful and sneaky, Hotep-Ra was eventually defeated by Tucker when he realized he had been used by Hotep-Ra.
Kitty Kitty (voiced by
Chynna Phillips) is Johnny 13's ghostly girlfriend. She is constantly under dire stress over Johnny, wishing he would focus his full attention on her. She has attempted to make him jealous and at several points, banished him to an alternate dimension via her ghostly ability to send any man to another dimension with a kiss. Despite it, the two remain in love with one another. In an alternate future depicted in "The Ultimate Enemy", she is married to the Box Ghost and has a daughter with him (Box Lunch).
Lydia Lydia (voiced by
Tara Strong) is Freakshow's assistant. She is heavily covered with tattoos, which she can bring to life and control, and is most often seen shrouded in a cloak.
Medusa Medusa (voiced by
Grey DeLisle) is based on the character of
Greek mythology of the same name. In "Boxed Up Fury", she is one of the obstacles Danny must get past to reach Pandora.
Pariah Dark Pariah Dark (voiced by
Brian Cox) was the ruthless king of the Ghost Zone, until he was eventually captured by rebellious ghosts and sealed in the Sarcophagus of Forever Sleep, where he lay until Vlad accidentally awakened him. He immediately laid waste to both Amity Park and the Ghost Zone until Danny ultimately defeated him, using a power-enhancing suit to enhance his powers beyond their limits.
Terminatra Terminatra (voiced by
Grey DeLisle) is one of the fictional characters from the film
Trinity of Doom (a parody of
Freddy vs. Jason). Terminatra is a spoof of the
Terminator. Terminatra is brought to life by Desiree after Sam wished unknowingly that something bad should happen to Paulina before her party. Technus later gains himself an upgrade after absorbing large amounts of electrical energy, rendering himself with a new look and upgraded ghostly form referred to as "Technus 2.0".
Vlad Masters / Vlad Plasmius Vlad Masters, or
Vlad Plasmius, (voiced by
Martin Mull in the series and
Nicktoons Unite!,
Trevor Devall in
Nickelodeon All-Star Brawl 2), is the
archenemy of Danny. Vlad is a powerful half-ghost businessman and scientist whose twenty years of experience constantly one-up Danny's ghostly abilities. Serving as the main antagonist in the series, he vows to destroy Jack for giving him his ghost powers, which in the process injured him terribly and put him in the hospital for seven years with a fatal condition known as "Ecto Acne". He wrongfully blamed this for ruining his life; however, it was his own evil plots that were the real product of his own personality flaws and refusal to accept that Maddie would never love him (the three had been classmates at the University of Wisconsin-Madison). Vlad's love for the
Green Bay Packers and their linebacker
Ray Nitschke is attributed and added due to series producer and writer
Steve Marmel's fondness for them.
Vortex Vortex (voiced by
Dave Boat) is a psychotic ghost with the power to control the weather, a gift he considers to be an art form. He finds Earth to be a meaningless planet, and has wrought havoc on it throughout the ages. On a trial by the Observants for his reckless behavior, Vortex is freed by Vlad who used him to his own services. However, Vortex rebels against Vlad and conjures up violent weather all over the world until Danny defeats him, gaining and losing Vortex's climate control powers. Vortex can generate and control storms, and the weather in general, from creating typhoons to making heat waves hot enough to melt walls, floods and winds cold enough to freeze streets in ice.
Walker Walker (voiced by
James Arnold Taylor) is a strict vigilante and warden who runs the prison of the Ghost Zone. He enjoys law and order and often commands with an iron fist; whoever so much as disobeys one rule from his law and rule book is in giant trouble. To justify his cause, he often makes up the rule as he abides by them and is not above using dirty measures to keep the Ghost Zone clean and corruption-free.
The Guys in White The
Guys in White are a secret
governmental organization dedicated to eliminating ghosts and other paranormal beings. She is hot-tempered, which often clouds her judgment, but slowly starts to realize a world beyond the superficial. She briefly strikes a romance with Danny Fenton, but clashes often with his alter-ego. ==Ghost allies==