Bowser's been a little on the loose side lately, he's not always like this, but he seems rather "turned on" about something, which in turn leads him to unbutton his shirt, the shirt that is normally buttoned. He could simply be doing so because it's quite hot in the room he's in ("room" in this case, is a enclosed area with blue-ish walls and nothing else around XD ), or maybe, he's "interested" in doing something else. Dat face outta tell you something. I wonder what he's thinking right now.... ;)