People constantly assess you by comparing who you are today to their general expectation of you. If, for example, you are a generally happy person, then when you are having a bad day people will notice. If, on the other hand, you are surly most of the time, then people won’t see any difference if you have an off day.
You can use this phenomenon to your advantage by slowly but regularly lowering people’s expectations and then, suddenly and irregularly, raising them. If you are never clean shaven, for example, then eventually people will come to expect that of you. On the rare occasions that you do shave, you will receive comments like “Hello handsome”, “Who’s the new guy?” and “Seriously, show me some ID or leave immediately”. Don’t do it too often, though, as you will begin to create new expectations.