Cephalopoid

The Cephalopoids are a sapient extraterrestrial species, some of which are known to live hidden on planet Earth.

Biology
While their true appearance is not known, they have ocular gill sets which appear like vertical eyelids, blinking occasionally, presumably when they go short of oxygen.

They are capable of high speed and agility as well as the ability to climb vertical surfaces bare-handed.

Appearances

 * Men in Black (1997)