Said to display how easy it is for someone to do something
when a person is doing something socially unacceptable the person doing the act will say it as they do it.
1."far out that dude was dunking on you homos 'at will''
2. whilst reversing through a drive through he exclaims
When someone is fucking up and their superior notices that they are fucking up, said person is put on notice. This notice, which is essentially a warning, reminds the person that their superior can fire them, punish them, etc. Thus they are "at will" of the superior.
Tina doesn't do shit at work. She just sits around, surfs the web web, and talks to Rob. If she gets caught, she's going to be at will.