P.F. Chang's is a real line of Chinese-themed restaurants that is spoofed on South Park. Despite the restaurant specializing in Chinese food the chain originated in America.
It has been seen two times in the show. The first time it was seen was in "A Million Little Fibers". Towelie had a job there at the beginning of the episode. However, he was so high that he got fired.
In "Obama Wins!", it was mentioned briefly when Kyle Broflovski won a gift certificate for $5000 to the restaurant. The prize was for being the one millionth individual to mention the "General Tso's Chicken" joke. After winning, Stan and Kyle can be seen eating P.F. Chang's takeout on the sidewalk.