Alien (My Best Friend Is Invisible)

The Aliens from the Goosebumps My Best Friend Is Invisible book and episode are unnamed semi-Humanoid alien species.

Appearance
In the book, they have two heads with five red eyes, with the tops of their heads being covered in tendrils, antennas and suction pods rather than hair. The also have several long arms, and their skin is grey.

In the episode, the species looks near identical to that of Humans, except they have two eyes and a mouth on the back of their head they can reveal, allowing them to walk "backwards" forward.

History
At some point, the species invaded Earth and enslaved Humanity. Most of Human race were exported to their interstellar colonies, however some Humans developed invisibly tech to remain on Earth hidden from the invaders.

The aliens proceeded to live on Earth in manner nearly identical to that of Humans. It is not really explained if their nearly identical lifestyle too Humans was either something they already had prior to their arrival to Earth, or that merely stole this lifestyle from actual Humans is unknown, and it isn't clear if former/latter or both are true. Also the possibility that Human lifestyle within this storyline was much different to that of actual Humans.