from the Shmoo wiki page:
A shmoo is shaped like a plump bowling pin with legs. It has smooth skin, eyebrows and sparse whiskers—but no arms, nose or ears. Its feet are short and round but dextrous, as the shmoo’s comic book adventures make clear. It has a rich gamut of facial expressions, and often expresses love by extruding hearts over its head. Cartoonist Al Capp ascribed to the shmoo the following curious characteristics. His satirical intent should be evident:
They reproduce asexually and are incredibly prolific, multiplying exponentially faster than rabbits. They require no sustenance other than air.
Shmoos are delicious to eat, and are eager to be eaten. If a human looks at one hungrily, it will happily immolate itself — either by jumping into a frying pan, after which they taste like chicken, or into a broiling pan, after which they taste like steak. When roasted they taste like pork, and when baked they taste like catfish. (Raw, they taste like oysters on the half-shell.)
They also produce eggs (neatly packaged), milk (bottled, grade-A), and butter—no churning required. Their pelts make perfect bootleather or house timber, depending on how thick you slice it.
They have no bones, so there’s absolutely no waste. Their eyes make the best suspender buttons, and their whiskers make perfect toothpicks. In short, they are simply the perfect ideal of a subsistence agricultural herd animal.
Naturally gentle, they require minimal care, and are ideal playmates for young children. The frolicking of shmoon is so entertaining (such as their staged “shmoosical comedies”) that people no longer feel the need to watch television or go to the movies.
Some of the more tasty varieties of shmoo are more difficult to catch. Usually shmoo hunters, now a sport in some parts of the country, utilize a paper bag, flashlight and stick to capture their shmoos. At night the light stuns them, then they can be whacked in the head with the stick and put in the bag for frying up later on.
The original story

In a sequence beginning in late August 1948, Li’l Abner discovers the shmoos when he ventures into the forbidden “Valley of the Shmoon,” following the mysterious and musical sound they make, (from which their name derives). Abner is thrown off a cliff and into the valley below by a primitive “large gal” (as he addresses her), whose job is to guard the valley. (This character is never seen again.) There, against the frantic protestations of a naked, heavily bearded old man who shepherds the shmoos, Abner befriends the strange and charming creatures. “Shmoos,” the old man warns, “is the greatest menace to hoomanity th’ world has evah known!” “Thass becuz they is so bad, huh?” asks Li’l Abner. “No, stupid”, answers the man—and then encapsulates one of life’s profound paradoxes: “It’s because they’s so good!!”
Having discovered their value (“Wif these around, nobody won’t nevah havta work no more!!”), Abner leads the shmoos out of the valley—where they become a sensation in Dogpatch and, quickly, the rest of the world. Captains of industry such as J. Roaringham Fatback, the “Pork King,” become alarmed as sales of nearly all products decline, and in a series of images reminiscent of the Wall Street Crash of 1929, the “Shmoo Crisis” unfolds. On Fatback’s orders, a corrupt exterminator orders out “Shmooicide Squads” to wipe out the shmoos with a variety of firearms, which is depicted in a macabre and comically graphic sequence, with a tearful Li’l Abner misguidedly saluting the supposed “authority” of the extermination squads.
After the shmoos have been eliminated, Dogpatch’s extortionate grocer Soft-Hearted John is seen cackling as he displays his wares—rotting meat and produce: “Now them mizzuble starvin’ rats has t’come crawlin t’me fo’ the necessities o’ life!! They complained ‘bout mah prices befo’!! Wait’ll they see th’ new ones!!” The exterminator congratulates him.
However, it is soon discovered that Abner has secretly saved two shmoos, a “boy” and a “girl.” The boy shmoo, as a Dogpatch native, is required to run from the girl shmoo in the annual Sadie Hawkins Day race. (Shmoos are usually portrayed as gender-neutral, although Capp sidesteps this issue to allow the comic plot twist.) When he is caught by her, in accordance with the rules of the race, they are joined in marriage by Marryin’ Sam, (whom they “pay” with a dozen eggs, two pounds of butter and six cupcakes with chocolate frosting—all of which Sam reckons to be worth about 98 cents). The already expanding shmoo family is last seen returning towards the Valley of the Shmoon.
The sequence, which ended just before Christmas of 1948, was massively popular, both as a commentary on the state of society and a classic allegory of greed and corruption tarnishing all that’s good and innocent in the world. The Shmoo caused an unexpected national sensation, and set the stage for a major licensing phenomenon. In their very few subsequent appearances in Li’l Abner, shmoos are also identified by the U.S. military as a major threat to national security.

from the Shmoo wiki page:

A shmoo is shaped like a plump bowling pin with legs. It has smooth skin, eyebrows and sparse whiskers—but no arms, nose or ears. Its feet are short and round but dextrous, as the shmoo’s comic book adventures make clear. It has a rich gamut of facial expressions, and often expresses love by extruding hearts over its head. Cartoonist Al Capp ascribed to the shmoo the following curious characteristics. His satirical intent should be evident:

  • They reproduce asexually and are incredibly prolific, multiplying exponentially faster than rabbits. They require no sustenance other than air.
  • Shmoos are delicious to eat, and are eager to be eaten. If a human looks at one hungrily, it will happily immolate itself — either by jumping into a frying pan, after which they taste like chicken, or into a broiling pan, after which they taste like steak. When roasted they taste like pork, and when baked they taste like catfish. (Raw, they taste like oysters on the half-shell.)
  • They also produce eggs (neatly packaged), milk (bottled, grade-A), and butter—no churning required. Their pelts make perfect bootleather or house timber, depending on how thick you slice it.
  • They have no bones, so there’s absolutely no waste. Their eyes make the best suspender buttons, and their whiskers make perfect toothpicks. In short, they are simply the perfect ideal of a subsistence agricultural herd animal.
  • Naturally gentle, they require minimal care, and are ideal playmates for young children. The frolicking of shmoon is so entertaining (such as their staged “shmoosical comedies”) that people no longer feel the need to watch television or go to the movies.
  • Some of the more tasty varieties of shmoo are more difficult to catch. Usually shmoo hunters, now a sport in some parts of the country, utilize a paper bag, flashlight and stick to capture their shmoos. At night the light stuns them, then they can be whacked in the head with the stick and put in the bag for frying up later on.

The original story

In a sequence beginning in late August 1948, Li’l Abner discovers the shmoos when he ventures into the forbidden “Valley of the Shmoon,” following the mysterious and musical sound they make, (from which their name derives). Abner is thrown off a cliff and into the valley below by a primitive “large gal” (as he addresses her), whose job is to guard the valley. (This character is never seen again.) There, against the frantic protestations of a naked, heavily bearded old man who shepherds the shmoos, Abner befriends the strange and charming creatures. “Shmoos,” the old man warns, “is the greatest menace to hoomanity th’ world has evah known!” “Thass becuz they is so bad, huh?” asks Li’l Abner. “No, stupid”, answers the man—and then encapsulates one of life’s profound paradoxes: “It’s because they’s so good!!”

Having discovered their value (“Wif these around, nobody won’t nevah havta work no more!!”), Abner leads the shmoos out of the valley—where they become a sensation in Dogpatch and, quickly, the rest of the world. Captains of industry such as J. Roaringham Fatback, the “Pork King,” become alarmed as sales of nearly all products decline, and in a series of images reminiscent of the Wall Street Crash of 1929, the “Shmoo Crisis” unfolds. On Fatback’s orders, a corrupt exterminator orders out “Shmooicide Squads” to wipe out the shmoos with a variety of firearms, which is depicted in a macabre and comically graphic sequence, with a tearful Li’l Abner misguidedly saluting the supposed “authority” of the extermination squads.

After the shmoos have been eliminated, Dogpatch’s extortionate grocer Soft-Hearted John is seen cackling as he displays his wares—rotting meat and produce: “Now them mizzuble starvin’ rats has t’come crawlin t’me fo’ the necessities o’ life!! They complained ‘bout mah prices befo’!! Wait’ll they see th’ new ones!!” The exterminator congratulates him.

However, it is soon discovered that Abner has secretly saved two shmoos, a “boy” and a “girl.” The boy shmoo, as a Dogpatch native, is required to run from the girl shmoo in the annual Sadie Hawkins Day race. (Shmoos are usually portrayed as gender-neutral, although Capp sidesteps this issue to allow the comic plot twist.) When he is caught by her, in accordance with the rules of the race, they are joined in marriage by Marryin’ Sam, (whom they “pay” with a dozen eggs, two pounds of butter and six cupcakes with chocolate frosting—all of which Sam reckons to be worth about 98 cents). The already expanding shmoo family is last seen returning towards the Valley of the Shmoon.

The sequence, which ended just before Christmas of 1948, was massively popular, both as a commentary on the state of society and a classic allegory of greed and corruption tarnishing all that’s good and innocent in the world. The Shmoo caused an unexpected national sensation, and set the stage for a major licensing phenomenon. In their very few subsequent appearances in Li’l Abner, shmoos are also identified by the U.S. military as a major threat to national security.