I'll admit I have fallen asleep at my desk on occasion (I used to do it on the heated toilet seat when I got tired, but I got sick of falling off). These things happen. But the teacher opposite me manages to pull it off every single day.
She's the "special class" teacher, too. I've walked past that classroom and seen her asleep at the front of the class, asleep in a student's chair, and asleep in there alone with the Down's Syndrome girl (also asleep).