Goop

Goop is a Polymorph from the planet Viscosia.

Ben first transformed into Goop in the episode The Gauntlet, when battling against a Techadon robot.

Powers and Abilities
Goop is a shape-shifting, self-regenerating, almost indestructible green blob that weighs 200 pounds. Goop can wrap his slimy body around his foes and throw them around. Ben usually becomes Goop to avoid damage or needs a flexible form. Goop controls his slime with an Anti-Gravity Projector in a shape of a small UFO and if the slime and the UFO are separated at least two feet the slime will become inert until the UFO recollects it, though in recent appearances, it seems that he can move without it unless the button on it is turned off. The UFO can cause the slime to take any shape and even hover off the ground and nothing can cut through Goop and he can imprison someone inside of the slime, his UFO can also hover alone and cut enemies as seen from the wild Goop in Vengeance of Vilgax: Part 2, as seen in Good Copy, Bad Copy, Above and Beyond, and Primus. Also, if Ben loses his UFO when going through an obstacle, the Omnitrix will create a new one. Goop is also able to fire off his slime, which gains powerful acidic properties upon impact as proven in Simple. Goop can use his acid like abilities to pick locks just like in the episode Nor Iron Bars a Cage where Ben, as Goop, helps him and Gwen get out of the jail.

Weaknesses
As potent as Goop is, it is plagued by the weakness of being limited to the UFO controlling the slime. If it is so much as separated by Goop by more than two feet, or turned off, the goo goes completely inert. The UFO must fly back within close range of the goo in order to reanimate it. It was shown in Primus that Goop's anti-gravity disk can be turned off with a push of a button, causing Goop to become inert. This was shown when Vilgax was tricked by Ben to turn into Goop to get the Omnitrix back. This weakness is in the Ultimatrix, because as shown in one of the Ultimate Alien episodes, Ben uses an anti-gravity modifier (Goop's UFO) to keep a planet held together. Then Goop is sucked into the planet and the whole planet turns green. Later, he comes back in Ben form. This form is also not too popular with Kevin and Gwen, as they both think it's disgusting. This is/was not helped by the remark made by Ben in Vengeance of Vilgax: Part 2 ("It's a sewer, of course there's Goop down there.").

Ben 10: Ultimate Alien
Goop briefly appeared in the Ben 10: Ultimate Alien episode, Andreas’ Fault. Ben used him to pass through a dungeon cell. Goop then reappears in Hero Time to save Julie from Overlord.

Ben used Goop to escape his fans at the beginning of Deep. He was only able to get away with the help of Gwen and Kevin. Later when Aggregor stole the Anti-Gravity Projector that holds the water planet Pisciss together - really a piece of the Map of Infinity - Ben turned into Goop again to use his own in its place. Although Goop was atomized and spread throughout the planet's water, he was able to use this to pull the planet back together; he changed back into his human form right after returning Pisciss to stable condition. He made another brief appearance in Nor Iron Bars a Cage where once again he was only used to break out of a room. Goop has also made a short appearance in Viktor: The Spoils as king Xarion was scanning through the Ultimatrix while Ben was unconscious. It is possible that Goop could have been able to slip out the cuffs that were holding him because of his liquid-like appearance, but since Ben controls the Anti-Gravity Projector, and he was unconscious, Goop can't escape.b

Ben 10: Alien Force

 * 1) The Gauntlet (First Appearance)
 * 2) Darkstar Rising
 * 3) Good Copy, Bad Copy
 * 4) Undercover
 * 5) Birds of a Feather
 * 6) Vengeance of Vilgax: Part 2
 * 7) Fool's Gold
 * 8) Simple
 * 9) Don't Fear the Repo
 * 10) Single-Handed
 * 11) In Charm's Way
 * 12) Primus (Used by Vilgax )
 * 13) Above and Beyond

Ben 10: Ultimate Alien

 * 1) Andreas’ Fault (first re-appearence)
 * 2) Hero Time
 * 3) Deep (2x)
 * 4) Nor Iron Bars a Cage
 * 5) Viktor: The Spoils(unconscious)
 * 6) Revenge of the Swarm

Trivia

 * Many times it seems that the Anti-Gravity Projector is the actual alien, whilst Goop is the avatar, as in Vengeance of Vilgax: Part 2, Wild Goop's Anti-Gravity Projector could control itself and cut Swampfire's body parts.
 * He is the first alien that Vilgax ever transforms into.
 * When Vilgax transformed into Goop, despite the fact that the UFO produces Goop's speech, he could still speak when Ben turned off his artificial gravity.
 * Goop can fly as seen in The Gauntlet as when the Techadon robot shoots lasers at him, he flies up in his blob state.
 * Dwayne McDuffie has confirmed that the natural species of Goop does not have the anti-gravity projector on their planet due to its gravity intensity level.
 * Dwayne McDuffie has confirmed that if Goop's projector is lost, the Omnitrix/Ultimatrix makes a new one. In Nor Iron Bars a Cage, this is proven whilst slipping underneath a door, a squeeze which the Anti-Gravity generator could not have handled.
 * Goop's Anti-Gravity Projector isn't part of the normal Polymorph's (Goop's species) biology, this may be due to the difference of gravity between Viscosia (Goop's home world) and Earth.
 * It has been seen many times that Goop can freely change his molecular structure at will, causing him to change from burning acid or to a slimy blob.
 * Goop was the first of Ben's alien forms whose name comprised of only a single syllable.
 * Although he can shape shift, Goop's humanoid state appears to be his default shape. Interestingly, Vilgax's version of the alien was different, sporting different shoulders. In any case, this state is clearly the one reverted to to if no control is exercised. In Viktor: The Spoils, an unconscious Goop remains in humanoid shape, oddly not oozing out of his shackles.