What is causing my tongue to be brown and furry? kind of creepy.

"Black Hairy Tongue": This tongue condition occurs when the growth of the innumerable tiny bumps on the tongue ("filiform papillae) is faster than the natural process of exfoliation. Certain practices, such as rinsing with hydrogen peroxide and other oxygenating mouthwashes, can provoke this condition. Regular tongue brushing or scraping can keep black hairy tongue at bay.

Filiform papilla: There are thread like filiform papilla on the surface of your tongue which can stain from smoking, coffee, etc. In the extreme it can be called black hairy tongue.