Scud
A person that seems to be very attractive from a great distance, but when viewed at a close up or normal distance, the person is extremely ugly.  Common occurences of one being is a scud could be caused by a messed up grill (teeth); the appearance of facial hair, a new view from the side and/or back, or simply a mullet.
Check out that beautiful girl...Oh Wait!  It's a scud!  Run!