A Neptunian Slug is a type of slug found on Neptune. It is available in two colors, yellow and purple, and can be used in cooking. Elzar uses one in a recipe on his television show, Essence of Elzar. Neptunian slugs are best used fresh in recipes but can be bought canned, or as a cured meat in the form of shanks and chops, these appear red when on display. Purple slugs are noted for causing 'nightmarish' diarrhea, but can still be bought. While contained, the yellow slugs are about four times the size of a normal slug and quite docile. When let out of captivity however, they expand in size threefold and become highly aggressive, spouting sharp fangs. When dead and being prepped for cooking, salt should be avoided as the slug shrivels to half it's size and retains an unpalatable salty taste (however, this was only shown once, and may not be a feature of the slug itself as Bender used a pound of salt in that instance).
Yellow slugs are actually lime green with a purple stripe on their back. Unlike terrestrial slugs, these have eyes on the end of their feeler stalks. Purple slugs have been referenced, but not seen.