Goop

Goop is a Polymorph (a word meaning "many shapes") from the planet Viscosia (a play on viscosity).

He is a 200 pound viscous life form, shape-shifting, made of green goo, also made of acidic, controlled by an anti-gravity multiplier developed by Galvans, that resembles a small UFO, where his voice comes from, and also has sharp edges. This device allows him to take any shape and levitate; however, if the anti-gravity multiplier and the slime are separated by even a short distance, the slime will become inert until the anti-gravity multiplier recollects it, and also it has a button that shuts off the anti-gravity. Goop first appears to battles a Techadon in "The Gauntlet".

In "Deep" Goop used his anti-gravity projector to keep the Piscciss planet's gravity, and he kept his anti-gravity multiplier there, even when Ben returns to human form. Dwayne McDuffie says the Ultimatrix will generate another anti-gravity multiplier; he also said that polymorphs did not use an anti-gravity multiplier.

In Alien Force and Ultimate Alien, because of his slime body, the Omnitrix/Ultimatrix can be easily pulled off, reverting Goop to normal and decoupling the Omnitrix/Ultimatrix from the user. In Omniverse, the Omnitrix is on the Anti-Gravity multiplier, eliminating this weakness. He reappears in "Blukic & Driba go to Mr. Smoothie's" for fight Trompipulor.

He reappeared in the Ben 10 Omniverse episode "Blukic and Driba go to Mr. Smoothies".

Source: http://en.wikipedia.org/wiki/List_of_Ben_10_aliens#Goop

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