You beat me to it....was gonna say they will have hours of fun with a carrier bag....the problem with ferrets is they get bored quite quickly with toys etc so you are constantly trying to find new things to amuse them, ive hung mesh hanging baskets from the roof, pipes, logs, you name it....but a carrier bag, you will wet your knickers laughing at them
Ive never had one get stuck in a bag but im sure if they did their teeth and nails are more than adequate to free them.
If you dont have much room for a court build UP rather than out.
MOLL.
I second the plastic bag thing.....Ferrets