When a person accidentally poops while mooning someone, and the smell of their own feces causes them to make the stank face.
Cheryl had diarrhea, but had the sudden urge to moon Josh. While mooning Josh, Cheryl started to release her feces, and the smell caused her to express the stank face. And Josh experienced the full effects of the StankButt.
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.