Importing content from a legacy CMS into Drupal. Figuring out how to map the article categories to taxonomy terms at 5 AM on the morning we leave to DrupalCon2007 in Barcelona. Nasty cold. Headache. Stuffed nose. Afraid walls will be covered in snot when head explodes in about 10 minutes.
Sometimes, the stuff you see on your screen just stops to make any sense at all. Look at the silly monkey.