Martians are an alien species that live on Mars. They only appear in the episode "Out of the Picture."
The martians resemble green blobs, and the part of their bodies that attach to the ground is light-green. On top of their heads, they have a blue, curled antenna, along with multiple blue spots, and they have glowing yellow eyes with red pupils. They also have two arms, pink tongues and teeth.
When Squidward is sent to Mars to deliver food, he encounters three martians. He says that he has a delivery from the Krusty Krab, causing one of the martians to grab the bag, pull out a Krabby Patty, and eat it, commenting that it is "yummy, yummy."
Squidward, looking around, then comments that "this dump needs a true artist touch," angering a martian and making it eat Squidward. The martians then fly a spaceship back to the Krusty Krab and return a goo-covered Squidward there.
The martians bear a resemblance to Plankton, being a similar shade of green, having a yellow eye with a red pupil, and have antennae.