Lol nostalgia indeed! @Tych Pretty much. Instead of eyeball you have a rubber coated ball bearing that also happened to pick up all of the crud from your desk. And it would build up a layer of said crud on the X and Y axis rollers that you see him swabbing. Interestingly enough, most were still optical on the inside using little slotted discs that rotated pass x and y axis light sensors to track movement
What I did was wait until a friend left the computer then take the ball out of the mouse, so that when they came back they couldn't move the cursor and would think the computer was broken.