Programmers are like vampires. They're frequently up all night, paler than death itself, and generally afraid of being exposed to daylight. Oh yes, and they tend think of themselves (or at least their code) as immortal.
System Administrators are like werewolves. They may look outwardly ordinary, but are incredibly strong, mostly invulnerable to stuff that would kill regular people -- and prone to strange transformations during a moon "outage".