Biography
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. It could be someone who is just not trying hard to stay clean, someone who just seems to attract filth, or someone who actually revels in filth and grime. Could be a Trash of the Titans or own a Ludicrously Unwashed Object as well, but remember that this trope is about someone who is filthy on a personal level. This trope could also apply to animals who like to play in garbage and mud. They may additionally be terrified of taking a bath.
Though usually seen as an Always Male Trope, there are still a fair number of female pig-pens. However, if a female character is a pig pen, it's usually a surefire sign that she's also a tomboy, as most girly girls hate being gross, filthy, or unhygienic.
There is some Truth in Television to this, as people used to rarely bathe or keep themselves clean. But as inventions such as electricity, indoor heating and indoor plumbing became more commonplace, walking around in a large layer of grime became rarer. Still, those who prefer being left unhygienic, or are just too lazy to tidy themselves up, may even have a chance to end up going through what's called "mysophilia".
Named after the Peanuts character Pig-Pen (pictured), who was always surrounded by a cloud of dust and has been seen going from "perfectly clean" to "covered in dust" while walking down the road or — most absurdly — in a rainstorm. Also see Men Can't Keep House, Dirty Foreigner and Humans Are Smelly for a more fantasy-based variant. When this Trope is a defining trait of a villainous or otherwise evil character, see Uncleanliness Is Next to Ungodliness. A character who offsets bad hygiene with high intelligence is a Genius Slob. Filthy Fun may or may not come naturally to them. If the character's bad hygiene comes with an odour to match, expect commentary in the form of Stink Snub. They may be the victim of a Hated Item Makeover.
Do not confuse with Dirty Kid. Contrast Neat Freak.
If you were looking for actual dirty pigs, see Messy Pig and/or Perverted Pig.