Mr. Garrison's first name is Herbert. Ms. Garrison's first name is Janet.
The characters of Terrance and Phillip were created because Trey Parker and Matt Stone kept getting complaints about the show being "nothing but bad animation and fart jokes".
Cartman's mom is named Liane after Trey Parker's former fiancée. He caught her with another man, and so he named the promiscuous character after her.
The character of Butters was based on Eric Stough, the show's animation director.
In the original unaired version of the pilot, Trey Parker is credited as "Tupac Schwartz" and Matt Stone is credited as "M.C. Schwartz".
Eric Cartman's middle name is Theodore.
Butters was originally named Poof Poof.
During the opening credits for the first two seasons, Kenny said something extremely crude. Trey Parker and Matt Stone were able to get away with this because his voice was muffled and very few people could make out what he was saying.
When the Production company logo appears at the end, the music that accompanies it is from the song "Shpadoinkle" from Trey Parker's student film Cannibal! The Musical (1993) (aka Cannibal! The Musical).
The character of Chef is based on an actual dining hall worker at the University of Colorado, the college Trey Parker and Matt Stone attended.
The character of Mr. Hat is based on a children's story book character called High Hat, which is a puppet that teaches children the letters of the alphabet.
Mr. Garrison is from Arkansas.
The famous South Park Holiday Special episode features live-action footage after every commercial break of Trey Parker as a newsreader saying "Fight the frizzies. Film at 11." This references a widely-circulated bootleg video of the infamous The Star Wars Holiday Special (1978) which included "pause button delay" sound bites of a real newscaster saying just that.
There is either a celebrity impersonator or mention of a celebrity's name in every episode.
Chewbacca is a running theme in the series. Every Halloween episode, at least one child dresses as Chewbacca, and usually wins the costume contest. Also, "the Chewbacca defense" is always used by Jonnie Cochran.
The pilot episode was made using paper cutouts of the characters. Every episode thereafter was animated with a computer
Tweek has appeared numerous times, and was the replacement Kenny in the second half of Season 6.
The music usually played over the closing credits is just the original opening theme song by Primus, only instrumental and slowed down.