Mark Brown is an American adult who was an enemy of Timmy Turner & others, while he's a good friend of Denzel Crocker & the L.O.S.E.R.S. in "The All New Fairly OddParents!". He was one of the more minor villains.
Mark Brown's appearance is generally described as "mysterious". His face is usually never seen, he usually wears a brown trench coat, black pants, a brown fedora hat, and a mask to cover his face. Under the mask, he was bald, with a small black beard.