Pig-Pen is a character in the comic strip, Peanuts, by Charles M. Schulz. He is a young boy who is, except on very rare occasions, very dirty. "Pig-Pen" is known for the cloud of dirt and dust that follows him wherever he goes. When he takes a deep breath (to sing, for example), the dust rises briefly around him. He sometimes refers to the cloud that surrounds him with pride as the dust of ancient civilizations. He cannot seem to rid himself of the dust for more than the briefest of periods--indeed, in spite of his best efforts, it appears that he cannot stay clean. He is referred to in an early strip as the only person who can get dirty while walking in a snowstorm. Nevertheless, on rare occasions he has very briefly appeared clean, and hence unrecognizable. Once this was in order to impress Violet, of whom he was a bit fond.
In "No Meals on Wheels", Violet Gray and Pig-Pen see Stewie Griffin, who was running Lucy van Pelt's psychiatry stand.