Grey Matter

Appearance
Grey Matter is a gray-skinned, frog-like, bipedal alien, only six inches tall with large green eyes with little minus sign like pupils.

Grey Matter wears a white jump suit with a black stripe going down it.

In the original series, Grey Matter wore the Omnitrix symbol on his back. In Ultimate Alien, his eyes are a lighter shade of green and he wears the Ultimatrix symbol on his chest.

Gwen as Grey Matter has Gwen's hair and has more oval shaped eyes with much smaller pupils. She wears a light blue jump suit with dark blue sleeves. She wears the Omnitrix symbol on her back.

Powers and Abilities
Grey Matter's size belies his great calculative and technical intellect. He can create almost anything from spare parts and know the function of any device at a glance. Grey Matter's intellect serves as a problem solver and analytical help in difficult situations.

Grey Matter can sometimes manipulate living things by stimulating certain parts of their anatomy, if such beings can be controlled by external stimuli.

Grey Matter's size allows him to squeeze into small spaces and he can climb walls thanks to tiny suction cups on his skin. He also has sharp teeth and his slimy skin makes him difficult to grab.

Grey Matter appears to be stronger than he looks, as he was strong enough to move a cleaner's bucket with mops in it in Ultimate Weapon.

Weaknesses
Grey Matter's size makes him unsuitable for battle, so he must outsmart his enemies in a fight.

Animals like dogs can pose a problem, as they may see Grey Matter as food or a toy.

Ben 10 and Ultimate Alien

 * Grey Matter first appeared in Washington B.C., Grey Matter was searching in cereal boxes for a Gold Sumo Slammer card.
 * In Hunted, Grey Matter defeated Kraab and Sixsix.
 * In A Small Problem, the Omnitrix malfunctioned, trapping Ben as Grey Matter for most of the episode. Grey Matter snuck onto a water slide and got captured by Howell Wainright.
 * In Secrets, Grey Matter appeared when the Omnitrix malfunctioned. He defeated one of Vilgax's drones.
 * In Truth, Grey Matter defeated a Null Guardian.
 * In Grudge Match, Grey Matter defeated one of Slix Vigma's drones.
 * In Ultimate Weapon, Grey Matter snuck into a house, let Gwen and Max come in and opened a safe.
 * In They Lurk Below, Grey Matter saved a drowning man.
 * In Ghostfreaked Out, Grey Matter appeared.
 * In Back With a Vengeance, Grey Matter appeared 8 times.
 * In Midnight Madness, Grey Matter was hypnotized into being Gwen's slave.
 * In Merry Christmas, Grey Matter accidentally destroyed the Rustbucket's air conditioner and later destroyed the Jingleator.
 * In The Unnaturals, Grey Matter appeared.
 * In Be Afraid of the Dark, Grey Matter escaped Zs'Skayr and built a sungun.
 * In Perfect Day, a dream Grey Matter defeated a mutated dream Cash and J.T.
 * In Ken 10, an alternate timeline Grey Matter was used by Kenny to escape his room and later, to unlock his Omnitrix's Master Control.
 * In Ben 10: Secret of The Omnitrix, Grey Matter defeated Dr. Animo.
 * In Ben 10: Race Against Time, an alternate timeline Grey Matter caused trouble in a diner.
 * In Snack Break, Grey Matter failed to retrieve his snack in a vending machine.
 * In Ben 10,000 Returns, Grey Matter was re-unlocked by Ben 10,000.
 * In Double or Nothing, Negative Grey Matter explains that he won't attack Ben, Gwen or Kevin anymore. Until it is revealed Albedo can only be Negative Grey Matter for about a second before reverting back.

Ben 10

 * Washington B.C. (first appearance)
 * Hunted
 * A Small Problem (accidental transformation; selected alien was Ripjaws)
 * Secrets
 * Truth (accidental transformation; selected alien was Four Arms)
 * Grudge Match
 * Ultimate Weapon
 * They Lurk Below (accidental transformation; selected alien was Ripjaws)
 * Ghostfreaked Out
 * Back With a Vengeance (8x) (last time was an accidental transformation)
 * Midnight Madness (under hypnosis)
 * Merry Christmas (2x) (last time the selected alien was Four Arms)
 * The Unnaturals (accidental transformation; selected alien was XLR8)
 * Be Afraid of the Dark (accidental transformation)
 * Perfect Day (accidental transformation; selected alien was Heatblast)
 * Ken 10 (used by Kenny Tennyson)
 * Ben 10: Secret of The Omnitrix (accidental transformation; selected alien was Stinkfly)
 * Ben 10: Race Against Time (accidental transformation; selected alien was Four Arms) (Race Against Time Timeline version)

Ben 10 Shorts

 * Snack Break

Trivia

 * As shown in Ken 10, Grey Matter is smart enough to unlock the Omnitrix's Master Control.
 * It was revealed that neither Azmuth or Albedo were where Azmuth got Grey Matter's Galvan DNA sample from.