Grey Matter is a grey frog like alien. He is about 6 inches tall. He wears a green jumpsuit with a black collar and belt. He wears black gloves with a green rectangle and has the Omnitrix on his back.
- Grey Matter has a superior intellect and can create almost anything from spare parts and know the function of any device at a glance.
- His size allows him to squeeze into small spaces.
- He can climb walls due to suction cups on his skin.
- Grey Matter's skin is slimy so he is difficult to grab and he has sharp teeth.
- He has enhanced strength for his size
- He is amphibious.
Grey Matter's size makes him nearly useless in physical battle so he has to outwit his opponent. Large animals can see Grey Matter as food or toy making them a problem.
- Washington B.C.
- Gwen 10 (by Gwen)
- Grudge Match
- Ultimate Weapon
- They Lurk Below
- Ghostfreaked Out
- Back With a Vengeance (x8)
- Midnight Madness
- Merry Christmas (x2)
- The Unnaturals
- Be Afraid of the Dark
- Perfect Day
- Ben 10: Secret of the Omnitrix
- Ben 10: Destroy All Aliens
- Snack Break
Ben 10: Omniverse
- Have I Got a Deal For You
- So Long, and Thanks For All the Smoothies
- Of Predators and Prey: Part 2