This is my attempt to clarify matters.
When one gets home from one's day job and is ready to plop down in front of the computer for some quality writing time, one dons Writing Pants (please see photo). Note that it is generally still light out and dinner has not been made, nor even thought of, at this point.
A bit later, after at least three separate parties have inquired as to the whereabouts of dinner, it's recommended that one change into one's Driving Pants (please see photo) before hopping into the car and heading to the nearest drive-through.
After dinner, when one's tummy is full and the house starts to turn a bit chilly, one generally opts for Comfy Pants (please see photo). It's worth mentioning that comfy pants, though clearly distinguishable from writing pants, are also entirely acceptable attire for writing.
Finally, when the rest of the house is asleep and one intends to be at the keyboard into the wee hours of the morning, it's the time to slip into one's Pajama Pants (please see photo). In case there were any doubt, these should never be worn out of doors (although a quick trip to the mailbox is fine) or when it's light out (an exception is made for snow days) or when company is expected (unless they live within a 15 mile radius).
So there you have it--a definitive, illustrated guide. Multiple choice quiz on Friday.