It's a konnyaku or shirataki noodle, made from the konnyaku yam (a kind of mountain potato, a.k.a. "devil's tongue"). The texture is like nothing else you've had -slippery, gelatinous, resilient, and crunchy all at the same time. Virtually flavorless on its own (but absorbs sauce and seasoning well), fat-free and low calorie (considered a "diet" food in Japan and other Asian countries), rich in fiber, gluten-free, and apparently helps eliminate toxins from your body by cleaning out your intestines (and often referred to as the "broom of the body" in Japan).
Whenever I have shabu-shabu (Japanese hot pot) at home, I like to include konnyaku noodles in my ingredients for the sheer novelty factor, especially when I have friends over who've never tried it before. I usually have a package of these noodles in my fridge (keeps forever) and it came in handy yesterday when I was too lazy to make rice for my leftover ma po tofu. I ate half the package of noodles - a 5 oz serving was only 50 calories, zero fat, with 8 grams of dietary fiber! And I definitely needed some detoxing after that Irish Soda Bread Showdown.
Konnyaku is also used to make jelly candy. The texture of the candy is similar to gelatin, however, it won't dissolve like jello and cannot be swallowed whole. This poses a major choking hazard to children and the elderly. Candy manufacturers in Japan responded to the recent public outcry by simply increasing the size of the warning label on the packaging.
You can find konnyaku noodles in the refrigerated section of Asian food markets. Try it for the texture - it's bizarre!
As for the "jellies that choke", I know I used to have some in my pantry a few years ago, but they're long gone. I don't remember having any choking issues while eating them, but if you ever should encounter them, please remember to chew! Not sure whether konnyaku jellies are still banned by the FDA but I'll check for them the next time I'm at my local Asian mart. Stay tuned...