The shmoo first appeared in Li'l Abner in 1948. The wonder of the shmoo was that it laid eggs, gave milk, tasted like whatever you wished, dearly loved to be eaten, and multiplied like tribbles. Every part of a shmoo could be used for a practical purpose: its whiskers as toothpicks, its eyes as buttons, its skin as leather, its flesh as lumber. The result of the discovery of shmoos, however, was misery; faced with a limitless supply of these miraculous creatures, people stopped working and society broke down. So the shmoos were exterminated. The shmoo inspired a wide range of shmoo-shaped merchandise in the 1940s and 1950s, now very collectible. (source: www.lil-abner.com/shmoo.html)
Eva Zeisel, a midcentury modern designer of pottery, dishware, and furniture, is also known for the beautifully organic shapes of her creations. She designed a pair of nesting salt and pepper shakers, epitomizing the design of this era, that are often referred to as "shmoos" because of their resemblance to these creatures.
Gloop and Gleep from the 1960s cartoon The Herculoids always reminded me of shmoos as well, in their non-elongated resting state.