I am a fucking genius

OK, so I'm lucky enough to have a job where I am often not in lab (library, other buildings, etc.). So if I want to leave and go home I just do. No excuse needed.
But I often think of you, gentle readers, and how you can get out of work when I send you home (to celebrate Head Days etc.).
Last night I came up with what I believe is the greatest "I need to go home from work" excuse ever. Lady Head disagreed and said I should post it and see what you think.
OK, here it is:
You disappear for about 5-10 minutes from your desk. You then walk into your boss's office, close the door, and say quietly "I just crapped my pants." Tell him/her that you had to throw out your underwear and need to go home.
Guaranteed to work.