"Planning a diarrhea" is a humorous way of referring to a planned sick leave from work, especially when it'
s not backed by actual sickness, but rather to spend
paid sick days for things other than sickness.
Diarrhea is used as an excuse for the leave, as it'
s cumbersome enough to keep one from leaving home, warrants little explanation, and
may not require a doctor'
s note to justify the sick day, as it can go away on its own.