It happens time and again. You have had so much fun inhaling nitrous oxide from the whip cream in a can, that you used up all the propellant but not the actual whipped cream. What to do. The package warns heavily (even on the light cream container) to not puncture the can. But out of propellant you haven't anything to fear, but you should do it in a controlled environment. The best™ way to open your can is use the one thing in your kitchen that is designed to puncture cans, a can opener! Since whipped cream cans aren't designed to be opened, you have to hold the can opener so the blade is on the side, not top down as you would for opening canned beets. Proceed as expected, aka twist the twisty thing on the can opener and wha-la! Whipped cream, ready and waiting for something to be plunked down on top of!