(There's no video for Bill yet. Please contribute to MR and add a video now!)
Bill is a window that you leave open on your screen that displays a crazy looking cat that stares and follows your mouse cursor. Unfortunately, the window does not stay on top of other windows, therefore you will only see it if nothing's up front, but I'm sure this could be hacked using ResEdit, changing the window type to a floating always on top window.
Bill.sit (5.29 KiB / 5.42 KB)
Bill the crazy looking cat that follows your cursor / compressed w/ Stuffit
Mac OS 6.x - Mac OS 9.2.2
Emulating this? It should run fine under: Mini vMac