Shnootyflopper
A fairly common disorder that causes those suffering to be unable to withstand the temptation of making societally-deemed inappropriate jokes, often in settings where they should not do so. Some popular examples include, "That's what she said", "Your mom", and so forth.
I'm sorry ma'am, I didnt mean to say your mom checks me out better than you check out my groceries, but I suffer from shnootyflopper.