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. Due to this, it is possible that at the very least, their eyes are Human-like. They are capable of high speed and agility, able climb vertical surfaces bare-handed while in a Human disguise, which could imply that they are truly humanoid beneath their disguises.

Appearances

 * Men in Black (1997)