A half-ghost, or colloquially among ghosts, a "halfa", is a human whose genetic structure is infused with ectoplasm. Half-ghosts have the ability to change between human and ghost forms at will, and possess the same supernatural powers that ghosts have. Though more have existed temporarily, there are currently only three known half-ghosts in existence: Danny Fenton, Vlad Masters, and Dani Phantom.
During Jack Fenton's and Vlad Masters's college days, Vlad became the world's first half-ghost when he was caught in the blast of Jack's prototype ghost portal. Twenty years later, Danny would go on to suffer a similar accident inside Fenton Works' completed ghost portal.
The only shown method of permanently changing a human into a half-ghost is when a human is exposed to an intense amount of ectoplasmic energy, such as being inside or near a ghost portal when it is activated, rearranging the human's molecules and genetic structure. This is how Danny and Vlad became half-ghosts. Other methods that were shown, but not permanent or reliable, include:
- A human can be enhanced with ghost powers from ghosts or ghost artifacts that grant wishes, such as Desiree or the Reality Gauntlet. This is how Tucker Foley briefly became half-ghost; however, Danny later separated the monster ghost that had overtaken Tucker from him with the help of the Fenton Ghost Catcher.
- A half-ghost can be created from an existing half-ghost using cloning technology, like Dani Phantom and the other clones of Danny that Vlad created. This is the only case where the half-ghost was not originally human.
- A half-ghost who has lost their powers can regain them if they are exposed again to an intense amount of ectoplasmic energy. This is how Danny got his half-ghost status and ghost powers back after losing them in "Phantom Planet," but the details of this process were never explained. However it possible the process is similar to how Danny and Vlad gained their ghost powers. When Danny got his ghost powers back it appears he also gotten an increase in his abilities as he used his Ghostly Wail with no ill effects.
Half-ghosts have immunity to many effects due to their dual nature. For example, they can pass through anti-ghost shields unharmed while in human form, and their ghost half makes them resistant to ghostly effects, such as Ember's hypnotic music, that would otherwise affect humans. However, like full ghosts, they are still vulnerable to ghost weaknesses such as ecto-ranium and Blood Blossoms.
- According to creator Butch Hartman, not everyone can become a half-ghost. There are limitations to the process and it appears DNA is limited in the transformation process. Hartman said that if Sam or Tucker had gotten caught in the Fenton ghost portal accident, it would have likely killed them.
- While Danny and Vlad’s ghost half are connected to their human half to a degree, it has been shown multiple times that one does not need the other in order to survive and one will not share the same fate if the other is "killed/destroyed".
|Species in Danny Phantom|
|Main species||Ghost | Half-ghost | Human|
|Other species||Alien | Clone | Cyborg | Demon | Dragon | Genie | Gorgon | Mummy | Robot | Siren | Unicorn | Werewolf | Zombie|