Mental Floss elaborates here on the technical aspects. Nice to know the specifics.
I figured as much with the flashing screen parts because there was a guy in my dorm who received an NES from his girlfriend. Although Super Mario Brothers and Konami’s Blades of Steel were more popular with our wing, we were curious about how Duck Hunt functioned. We fired up his VCR to record a quick game of it. Then we watched the tape back in slow motion. Every time the gun was fired, the entire screen went black except for white squares in place of the ducks. We were satisfied with that. Now the article fills in the gaps on the nitty gritty.
I wonder if Wii can do the same with its hardware.