How to remove spokes from a wheel (this should apply to all bicycle wheels and not exclusively fixed gear):
This video will show you the quickest and easiest way to remove spokes. For this, you won’t need a spoke key or wrench, just a pair of pliers.
Clearly this is a way to remove old spokes very easily when you are looking to get them off your wheel fast. You will still need to remove the tire and tire tube, and will potentially have to remove the cassette front he wheel as well if you plan on installing new spokes on the drive side of the wheel.