Nilian

Nilians are extremely tiny humanoids from the planet Nil who lack emotions (likely due to their culture not seeing it as a necessity towards existence). Very similar to humans, they come in a multitude of races or subspecies.

Background History
With their homeworld seriously threatened by an energy crisis of salt, the Nilians were forced to invade the planet of the "giants", Earth. To accomplish this, they first send a small sphere capable of draining the Earth's oceans to harvest the salt within (perhaps through black hole or teleportation technology). Despite their precautionary procedures taken by encapsulating the sphere into a small asteroid, it fails to meet quota. Fearing the worst, the Nilians built a human-sized spaceship in the likeness of its Captain-to-be, which was christened as "Dave". Once on Earth, the Daveship is damaged and soon, the Captain falls for a single mother named Gina Morrison.

Chaos ensues aboard the vessel as the crew witness human emotions, evoking the same sort of responses in their own species, which naturally are quite "boring". Some crew members begin to fear that a virus has taken over much of their allies, and that something must be done. Soon enough, the Captain is mutinied out of his own vessel, and his second in command, Number 2, takes the helm to wrought destruction and retake the sphere.

Eventually the Nilians decided that it is not worth the destruction of the Human's homeworld (and the subsequent extinction of all of its life) to save their own, and they move on to find another source of salt to utilize.

Speculation

 * It is not known why they didn't at least remove the salt from the Dead Sea, Great Salt Lake, or any of the various salt pans throughout the world, such as the famous Bonneville Salt Flats of Utah. It is possible they either did not know about any of these, or in the end chose not to harm Earth's ecosystems in any way, shape, or form.