He is phantom/ghostly alien with claw like hands. His skin is grey and has black lines running all over his body. When the skin is removed it will reveal his tentacles or his true form. When using his intagibility or invisibiliy power the Omnitrix turns the color of Ghostfreak.
The Omnitrix symbol is located at the center of the chains or on his chest.
16 yr. old Ben: He appears to now have green chains all over his front side that lead to his neck, waist and center/chest. The spikes on his elbows return and his skin is now a yellowish green. He wears cuffs on each of his arms.
11 yr. old Ben: He has a similar appearance to 16 yr old Ben but the chains are silver and he has flourescent skin.
Much like Big Chill, certain substances can neutralize Ghostfreak's intangibility and his invisibility. If Ghostfreak's second skin is taken off, he becomes sensitive to light and will be burned to death if exposed to too much of it. In the original series, Ghostfreak's DNA allowed him to regain his memories and personality, recreating Zs'Skayr, who took over Ben and freed himself after the Omnitrix timed out.
Ghostfreak is the second alien from the original 10 to make a re-appearance in Alien Force. The first was Diamondhead.
According to Ben in the original series, he was always creeped out when he was Ghostfreak.
Ghostfreak has a sense of smell, even though he has no visible nose, since he could smell a pie in Permanent Retirement.
When giving information on Ghostfreak, his creators said that before they started drawing prototypes, they decided that they wanted to make something like a genie. As time went on however, the idea and character design eventually became a ghost.
Ghostfreak was the last of the original 10 in the Original Series to make his debut.
Ghostfreak is the only alien to have different looks throughout all of the four series.