Slang usage describing one suffering from various mental illnesses, or really just about anything that makes them sufficiently different from the rest of society (see freak). Can be referred to as "a crazy", or plural, "crazies". An example of usage can be thus: "Have fun tonight, but watch out for all the crazies!". Alternating caps may be used to emphasize just how much of a CrAZy an individual is, if necessary.
The first time I recall hearing it phrased this way was from a damn hippy friend of mine while traveling. As we were passing a large building with mirrored windows and no identifying signs or symbols (which gave it a rather ominous appearance, he looked up and said, "I'll bet there's a CrAZy pressed against the back of every window in that place!".
Also, standard I'm-either-one-or-have-a-close-family-member-who-is-so-I-can-say-whatever-the-hell-I-want-about-it disclaimer applies.