Smudge is the rat that helped Namine escape from Dr. Mauls lab. During the process she also saved his life several times as well. Even though he technically doesn't owe her since they helped each other, he still acts as her servant, calling her Mistress and such. 

He's a rather large anthro/alien packrat creature that originally was used for experimentation in the Dr.s lab, hence the scars and missing eye. 

He's extremely dirty, for the most part, and hates baths. His fur would be a lighter color most likely, if not for all the dirt. 

He excels in 'obtaining' items, wether legitimately or not doesn't matter to him, though when he brings it to his master he tries to get it from sources that won't trace it back to him, or that are dead.

When he's not doing such, he is following Namine around, catering to her business needs, as her accountant and document keeper.