The Blob

The Blob is an amorphous, gelatinous alien entity that was brought to planet Earth trapped inside a meteorite. Nothing is known about its origins, the natural habits of the species, or how common they are in the universe.

This creature has no definite shape or size, being able to change its form at will. It quickly consumes all living things it can capture, digesting its prey chemically and growing more and more as it feeds. It also seems to be very fast and strong for a gelatinous organism that moves around by slithering. The thing was originally transparent white, but grew dark reddish purple from the blood of its victims.

Although there is no known way to kill a Blob, it is known that the beast stays away from cold temperatures, as they cause the Blob to solidify. It is not killed, though, and it will come back to life once the temperature is raised again.

The Blob (1958)
The Blob fell from the night sky and crash landed on Earth near an old man's cabin in the woods. When the owner heard the impact and came to investigate, he saw a ball-sized meteorite still intact in the crater. Just when he was using his stick to poke the space rock, the meteorite hatched and the alien-like Blob emerged from inside. Intrigued, he used his stick to poke the alien and bring it closer to him. The Blob attacked him by crawling up and covering his right hand, attaching to him. The old man tried to remove it, but to no avail, and screamed in pain, forcing him to retreat back to the woods and run down to the roads where he almost got hit by Steve's car. Steve and Jane picked him up out of the road and took to Dr. Hallen's house.

Steve and Jane quickly brought the old Man to Dr. Hallen, who sent the young couple to find any information about who the old man was and what was on his hand. Few moments later, the Blob was shown to be slowing digesting the old man's arm and the rest of his corpse. When Nurse Kate arrived to check on him, the old man had been already devoured by the Blob, who attacked the nurse. Hallen told her to throw acid at the Blob to kill it, but the acid had no effect. The Blob ends up devouring Hallen as well, and escapes to the nearby town where it consumes several other people.

Later, the Blob was frozen by citizens and firefighters using CO2 fire extinguisher. The Air Force transported the frozen creature away and abandoned in the Arctic Ocean.

Son of Blob (1972)
Fourteen years later, a piece of the Blob was brought back from the Arctic by a man named Chester, and it later consumed a fly, Chester's cat, Chester's wife, and Chester himself. After increasing in size, it was eventually frozen again. The Blob was last seen consuming a cop after being unfrozen again.

Trivia

 * The Blob seen in the 1988 remake isn't related to this creature at all, for it originated as a scientific experiment rather than being a genuine alien organisms. In the 1988 incident, the Blob was more intelligent, for it ambushed prey. It even trapped prey.
 * Some aspects of the Blob's biology (particularly its feeding habits) are somewhat reminiscent of the Slithersucker, a large and sophisticated species of slime mold which inhabits a future version of Earth in The Future is Wild.