Someone I know would constantly leave a macbook unlocked, so I prepared a script that would turn down the volume, whisper the owner's name, open weird sfw pictures online and other mildly annoying things, but not very often (like once a week).

This was meant as a joke, and I never actually went through with it. I know the person very well but it still felt douchebaggy. But the idea was to make an app file, save it to some seemingly legitimate folder, and adding it to the autostart list.

The trick to hide the thing was to drag and drop Safari's logo onto it, and naming the app "Safan": it almost goes unnoticed when checking the Activity Monitor, thanks to the system font's proportions.