A "Frat Fucker" is one who joins a fraternity... period. 99% of frat members or "brothers", are womanizing assholes who need to pay to have friends. Usually also have a small penis, or a weak personality, and use a fraternity to make themselves feel wanted or special.
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.