A good friend of mine does this kind of thing all the time -- he streams his glitching sessions on twitch.tv, but also takes screenshots of amusing results. I have a partial archive
here. He either uses a NES emulator that sticks random values into RAM or ROM parts, or uses a ROM corruption tool. If you need/want names of the tools/emulators he's using I can ask him.
Within certain niches of the Internet this is referred to as "glitching" (i.e. glitch videos).