Chad is a generally derogatory slang term referring to a young urban white man, typically single and in his 20s or early 30s.
The term originated during the 1990s in Chicago, Illinois, and was further popularized by a satirical website dedicated to the Lincoln Park Chad Society, a fictional social club based in Chicago's upscale Lincoln Park neighborhood.
The female counterpart to the Chad, in slang, is the "Trixie"
https://en.wikipedia.org/wiki/Chad_(slang)
Stacy is the name of every popular girl ever. See: Movies and IRL.
The name Stacy itself is "Barbie" but set for real world encounters. Chad and Brad are similar.