Atlantean (SpongeBob SquarePants)

Atlanteans are a sapient species of small aquatic aliens which came to Earth thousands of years ago and built an advanced civilization on the ocean floor.

Biology
Atlanteans are small creatures, comparable in size to SpongeBob and other inhabitants of Bikini Bottom. They are bipedal fish-like creatures with blue skin, red lips, four-fingered hands, a long thin nose and a short tail. The top of their skulls is transparent, exposing the brains. Some individuals have heterochromatic eyes.

Culture and society
Atlanteans are an advanced species with vast material wealth and unparalleled achievements in scientific, artistic and military fields. Their most treasured possession used to be a million-year-old bubble brought from their original homeworld, until the bubble was accidentally popped by Patrick Star. It was then replaced by a copepod named Sheldon J. Plankton.

Appearances

 * SpongeBob SquarePants, s05e12, "Atlantis SquarePantis" (2007)