Take a screen shot (print screen button) and open the image up in an image editing software program (Photoshop, Paint, etc). Use the paste feature onto a new image, crop/tweak from there and go ahead and save it as a jpg, etc.
Re: last night's episodeI think Cartman's version of Lady GaGa's "Poker Face" is the best South Park song I've heard in a long, long time.
I'd like to get back into this show, but I never seem to be able to catch it when it's on. I have all the DVD sets, but ya - that's a lot of watching at one time.
Or just watch any episode you want when you want for free at SouthParkStudios.com.