A dingle ball is a slang term for a popular cat toy which is a small ball of plastic with slots on the sides and a small bell on the inside. Popularly, cats will watch a dingle ball in motion, perhaps even chasing it a bit (if the cat is young enough and the ball is traveling far enough), but that's about the extent of their play with the things.
The exception to this rule, of course, is to be found when a human is sleeping. Or at times when there needs to be total concentration without outside interruptions. Then cats will find a dingle ball to be the most amusing thing in the world, and will be certain to play with it enough to create a veritable cacophony of sound. If you should chance to get up and go try and fetch the blasted dingle ball away from the cats for any reason, you will enter the room and find the cat lying in a resting or sleeping position, and the dingle ball nowhere to be seen.
DO NOT BE FOOLED BY THIS!
The cats earn extra points if they can get you to swear at them or else fool you into thinking that they weren't really playing with the dingle ball at all. The dingle balls get extra points for disappearing from your sight during the confrontation encounter. Nobody wants to lose possible points, and so the cats are merely faking.
To spoil their game plan and earn points yourself, I'd advise that you stare intently at the cat in question for a good minute or two. Watch their ribcage... if you see them panting, it's a sure sign you've found the culprit. To earn the points you need to say "AHA!" loudly enough to startle the cat into moving, in which case you may go back to what you're doing because you've won this round and the cats will be silent in shame. Do not be fooled by miauing or nuzzling. The cat may try to hold his breath in until you leave, so wait long enough to make sure that he has to start panting.
Always remember, though, the 2 points for a reversal can easily become a 4 point gain for the animal AND dingle ball if by shouting "AHA!" you succeed in waking someone else in the house who will complain at you, or if you are sleepy enough to startle yourself.