Housekeeping Zombies are helpful folk who fix/correct/tidy an environment through the application of (usually excessively mundane or tedious) labor. Housekeeping zombies are stealthy as ninja in the execution of their tasks, though they sometimes lack subtlety. Upon examining an area straightened by a housekeeping zombie, it will be unmistakable that something has been done, but it will seldom be clear exactly who did it.
Housekeeping Zombies are WikiGnomes who are particularly fond of DrudgeWork?. Or perhaps, they see that the value of the completed DrudgeWork? is more than the value of the time it takes.
The existence of Housekeeping Zombies was first postulated to explain how, in a house full of none but the undead, items moved in a room would be found returned to their original positions if left unobserved for more than a few seconds.
You may see other evidence of their existence on the Wiki, for example, "I started putting the tabs back in on this page, but I'm tired of this game now. Sorry." found half way down some page full of accent characters and tabs.