Sarcasm sign
From The Big Bang Theory Wiki
Sheldon just doesn't 'get' sarcasm. When Leonard in exasperation said, 'For God's sake, Sheldon, do I have to hold up a sarcasm sign every time I open my mouth?', Sheldon replied, intrigued, 'You have a sarcasm sign?' ... totally missing the sarcasm.
image: http://gallery.the-big-bang-theory.com/displayimage-320.html
