Suggesting this is a way of saying someone is talking or acting crazy. Used to express disbelief, skepticism, or simple mocking. Indicates a level of ridicule serious enough to move the subject away from what the other person has said, and onto the state of mind of the speaker.
"If you think you can get away with driving 50 more miles with the 'Empty' light on, you need a checkup from the neck up."
An aggressively stupid person. A true schmoe-donkey combines the hapless, clueless, luckless qualities of a regular schmoe with the stubborn, clumsy qualities of a class-A jackass.
"Who was that random guy at the party?"
"You mean the one drinking all our beer?"
"Yeah, and hitting on all the women, even though they told him to piss off... for like three hours straight."
"Oh, that guy? Yeah, just some schmoe-donkey."