Fan Casting The Pig-Pen in Sort by Tropes

Yuck! A character whose most obvious trait is that they are absolutely filthy. Not filthy in morals, behaviors, or ethics (but sometimes they are), but someone whose body is actually covered in filth. The person might have other qualities as well, but their filthiness is bad in relation to the rest of the cast, or at least the setting. Chances are that they may look just as bad as they smell, and bonus points if every nearby living being withers away from the foul odor they radiate.