Playing dress-up

I should probably try to come up with a Halloween costume soon. Any thoughts?
Here are the requirements:

1. comfortable. This is mandatory.
2. cheap. $0.00 is the preferred expenditure, although I've gone as high as $25 in the past.
3. vaguely workplace-appropriate. I'm only dressing up for work.
4. apparently, this year we're adding slap-dash to the list since I have only a day to throw this together.