There are a few things you can do to remove poop stain from a car seat. The first is to use a mild soap and water to clean the area. This will help remove any built-up bacteria that may have been left behind. The second step is to use a vacuum cleaner and bucket to suck the poop out of the seat. Be sure to do this in an even manner, so as not to damage the fabric of the car seat. The third step is to use a dryer sheet and heat up the dryer until it starts making noise. This will help remove any excess moisture that may have been left behind.