When at a hot, crowded concert you take your sweaty t-shirt off and swing it around your head in an attempt to show enthusiasm for the music and it sends out a rank wave of BO to all innocent bystanders.
At Lollapalooza lots of hot, sweaty guys were smellycoptering at the Killers concert. Unfortunately some of them were so enthusiastic I got smellycoptered in the face.
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.