They write, perform and animate each show in only a week's time. They don't build a back-log of shows; each show is freshly made and is aired within only a few days after completion. This impresses me very much.
It's best, as with any sitcom, to start with season 1 and work your way up. Each season has it share of winners and episodes that aren't the greatest but are still worth watching. I cannot honestly pick one season over another.
My very favourite episodes are PETA and Erection Day.
Always enjoyed Mrs Crabtree, the school bus driver. That character ended when the lady who voiced her committed suicide.
The movie Team America is a classic. I wasn't expecting it to be. Didn't think much of it until the song America! F**k Yea! started playing. A tiny grin began to spread across my face, increasing in size and speed like a paper towel soaking up a spill, until I burst out laughing.
Parker & Stone are the rare Americans who not only can take the piss out of USA culture & politics, but can do so without coming off like hippies or leftists.