well you need the episodes off a dvd or downloaded (id recommend DVD to keep it legal)

then you also need a video editing program like sony Vegas or Adobe premier (both have inexpensive versions made for home use if you dont want pro) Oh wait if you have Windows you can use windows movie maker (the vista one is better than xp, but either will do)

then youd get whatever you want off the episodes. Other than that you can get a screen recorder program and record some vids that you watch on your PC to obtain clips. you still need a movie editor though.