Undergrowth is a villain who appears in "Urban Jungle." He wants to wipe aside humanity for their careless destruction of nature.
Undergrowth first appeared in "Urban Jungle". Angered that the people of Amity Park were destroying his children for urbanization, he attacked and used mind vines to turn everyone into his slaves. With Sam turned into his "daughter," he had her attack Danny.
However, Danny managed to escape with his new ice powers. Sometime later, Danny returned, having finally mastered his ice powers thanks to Frostbite. Using it, he managed to destroy Undergrowth's new plant world by defeating Undergrowth, he was reduced to a shrub and destroyed by Tucker's lawn mower.
He has a cameo in "Boxed Up Fury", in which the Box Ghost finds a reward for Undergrowth, claiming that he's an overgrown ficus.
Undergrowth's next and final appearance was in "Phantom Planet". He first appeared earlier, when Danny battled him in an attempt to prove his superiority to the "Masters' Blasters", only to fail and for them to capture Undergrowth.
Undergrowth is depicted as a giant, vaguely humanoid being apparently composed of plant-matter in the form of vines with a face. He has red eyes, darker green hands, shoulder pads, a green cape, and four spikes on his head. His mouth resembles a spiky bird beak, which is probably where the nostrils are as well.
Undergrowth favors plants over animal life. To him, they are his "children". He sees humans as fragile, temporary lives that won't last long. He prefers using humans to do his dirty work. Undergrowth often snarls sometimes before he begins a sentence, similar to Vortex's mid-sentence wheezing.
However, he does show some respect to humans who want to help nature, such as Sam. He is also very proud of his own power, especially regeneration.
Despite his hatred of humans, Undergrowth did sense that Sam was helping nature; as such he "replanted" her, and remolded her mind to think of him as a "father" and to help him look after his plant children.
Undergrowth sees Danny as his main enemy and a threat for his goals of world domination, as such he wants to feed him to his plant children.
Undergrowth is easily one of the strongest ghosts ever and said to be nearly impossible to defeat. Despite lacking the standard ghost powers/abilities he developed Intangibility and Flight in Phantom Planet. Many of his powers are derived from his control over plants.
- Chlorokinesis: As the ghost of plants, Undergrowth can completely control all types of botanical life. He can also manipulate them and speed up their aging process, causing, acorns to become fully grown trees in seconds, and a city to transform into a jungle in a few hours. These plants are shown to be directly linked to him, as when he was defeated, they die. His control is presumably on a global level. Undergrowth can create and manipulate all types of different plants, to the point where he can create new types of plants, never seen before, like giant venus flytraps and giant cactus men.
- Mind Control/Sentience Infusion: Undergrowth can use Mind Vines to take control of humans, and also brainwash humans to join him, while retaining their personality, only becoming his minion. It may derived from his overshadowing, if he has it. He can make plants sense, see and move on their own, although he can still control them, if the need arises. He can infuse other creatures, be it humans or ghosts, with some of his powers, as he did to Sam.
- Sleep Inducement: In "Urban Jungle", Undergrowth produced spores that put others to sleep. He did to put Team Phantom to sleep so he can capture them.
- Regeneration/Root Form: He is one of a small number of ghosts that can easily regenerate lost body parts and reform after being blown or shattered into pieces. After being blown up by Danny's explosive snowball, he shrank into the Earth, then regrow in a different place, thus giving him a sort of teleportation. However he eventually regrew after being reduced to mulch by Tucker's lawnmower.
- Supernatural Strength: Undergrowth is capable of ripping solid concrete like paper, crushing trucks like tinfoil and bring down entire buildings with nothing but his might.
- Spectral Body Manipulation: Standard ghost power. As a plant he can stretch, bend, and twist as necessary. Since his body is a plant Undergrowth is able to manipulate the vines wrapped around his body, and use them as extra limbs or grow to enormous sizes in seconds. His vines are also strong enough to easily crash trucks and cars and hold ghosts, as Danny's strength couldn't even tensed them. His vines can also control ghost energy, as Danny couldn't use his energy blasts or intangibility, when he was kelp in his vines.
- Duplication: He could cause multiple versions of himself to grow, providing him with duplicates, only they all shared one mind.
- Spike Generation: Besides of having them on the vines that surround his body, he can throw them as projectiles, and they are strong enough to pierce concrete and brick walls.
- Ice/Cold: His main weaknesses is extreme cold (and assumable fire/heat) due to his plant-like appearance. Danny's freeze powers weakened Undergrowth completely. His roots and brain are also his main weak spot, causing him to shrink when they were frozen. Also, when destroyed he will revert into a weed-like state that might take a long time to return to normal. When last seen at the end of "Urban Jungle," he had managed to regenerate into a small, rudimentary form despite his earlier defeat at Danny's hands, only to be reduced to mulch by Tucker's lawnmower.
- "ARGH!! Flesh-dwellers, you have caused pain to my children once too often!"
- "Now you too shall feel pain... the pain of Undergrowth!"
- "Pitiful human race, your "progress" has destroyed acres of my children, now I shall destroy you to make room for my new offspring!"
- "You can't destroy a being who's able to regenerate himself!"
- "Ugh, such limited lifeforms. Although instant destruction is an option... I feel the replanting will be more "productive"!"
- "Rejoice, for a new era is taking root!"
- "Yes, the growth is far stronger than any meat creature, no matter how powerful they think they are."
- "Perhaps one day you will see that this is what nature intended all along."
- "Mankind is merely a temporary weed in the garden of life... a weed that can be removed."
- "Your pessimistic, but accurate friend, is right. Observe, your once proud progressive metropolis."
- "The mind vine enables me to control the inhabitants' every movement. Why should I burden myself with the destruction of your city, when I can have its own citizens do it for me?"
- Undergrowth is one of the few evil ghosts that have never been seen being caught in the Fenton Thermos, but rather destroyed right on the spot.
- Undergrowth is voiced by legendary actor Mark Hamill, who is well known for roles like Luke Skywalker from the very first Star Wars movies, and The Joker in most media featuring Batman (the latter of which found him a niche in the world as the voice of "powerful" villainous characters, like Firelord Ozai from Avatar: The Last Airbender, Malefor from The Legend of Spyro: Dawn of the Dragon, Darth Bane from Star Wars: The Clone Wars, etc.).
- The word ''Undergrowth'' describes a dense growth of shrubs and other plants, especially under trees in woodland.
- Undergrowth also serves as the main villain of Danny Phantom: Urban Jungle, a game based on his debut episode.
- As for the type of ghost Undergrowth may be, it's highly possible that he's a dryad, a powerful, territorial, and sometimes formidable nature spirit of Greek mythology that holds domain over forests, jungles, and other various woodland environments. To further strengthen this hypothesis, the wrath of a dryad can vary depending on what crimes against a forest a person is guilty of, but it is never pleasant.
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