Three-Armed Martian

The three-armed Martians are an unnamed sapient humanoid species with three arms who attempted to colonize Earth, only to be intercepted and possibly exterminated by three-eyed Venusians.

Biology
The three-armed Martians appear almost entirely identical to Humans, except for the presence of a third arm, located on the right side of their bodies, directly under their "normal" arm. Most other physiological differences from Humans are unknown, but due to their lack of knowledge of most of water's properties, likely due to the lack of water on Mars, it is extremely likely that they are hydrophobic, and water is definitely not a chemical solvent used by this species. Despite evolving in the Martian environment, they are perfectly capable of surviving in Earth's environment.

Culture and society
The three-armed Martians sought to colonize Earth, sending at least one advance scout to ensure Earth was ready for colonization, who held no qualms towards killing Humans to preserve his identity. In addition, they appear to have been watching Earth for long enough to know about several aspects of Earth culture, such as the corporate world, Boston, and various Human technologies. It is unknown if they wished to colonize Earth with a frontal invasion force, or by infiltrating it by disguising as Humans until there were enough of them to enact a takeover. Due to their unique physiology, their clothing, even the Earth-styled business suits their infiltrator wore, have a third sleeve for their third arm, identical to their other two sleeves. They are capable of hiding their third arms, presumably using another garment or possibly some sort of cloaking technology, in order to pass off as Humans. Due to their origin, they do not know much about water, such as what the definition of "wet" is. They appear to have had a hostile relationship with the three-eyed Venusians.

Technology
The three-armed Martians possessed a colonization fleet and smaller spacecraft capable of crossing from Earth to Mars. They also appear to have technology that can cast visual and auditory illusions, or control machines, making power fluctuate, devices randomly activate, fake a phone call, and somehow cause sugar dispensers to explode.

History
In the 1960s, the three-armed Martians sought to colonize Earth. Observing Earth and assembling a colonization fleet, the Martians send an agent to Earth to ensure that Earth was ready for colonization. The agent lands his ship in a frozen pond somewhere in the northeast US, and quickly exits, taking on the disguise of a businessman with the name of Ross. He quickly makes his way to the nearest Human establishment, a diner called the Hi-Way Café. A bus had parked outside, with its driver, Olmstead, and six passengers entering the diner during a heavy snowfall. Ross manages to join the group as they enter, with no one noticing him. Two state troopers who saw the landing site soon arrive, and notify the passengers that the bridge ahead is closed until approved to reopen by the county engineer. Unable to return to their previous stop due to an icy hill, the passengers would be stranded in the diner, and Ross expresses his discontent, taking on the personality of a grumpy businessman and claiming to be on his way to a meeting in Boston that he cannot afford to miss. The troopers also say that there is alien possibly among the passengers, as Olmstead only remembers there being six passengers, and yet seven were present in the diner. According to the cook, a man named Haley, he has had no other customers for several hours before the group arrives. The troopers and passengers debate, the two couples, Olmstead, and a woman named Ethel who Olmstead remembered being on the bus being excluded from suspicion, leaving just Ross and an eccentric old man named Avery. Ross, through an unknown and unseen manner, makes the jukebox go off and several sugar containers explode. However, the troopers are unable to determine who is the alien, and Ross fakes a call from the county engineer clearing the bridge as safe to travel over. The passengers board the bus again, and the troopers volunteer to escort them. However, the bridge was actually unstable, collapsing under the weight of the vehicles and killing the Humans, although Ross escapes, possibly by jumping out of the bus before it plummeted. He returns to the diner, and tells Haley about what happened, revealing his third arm and bragging about his species' plan to colonize Earth. However, Haley is merely amused by these revelations, and reveals that the Martian colonization fleet has been intercepted and presumably destroyed by the Venusians, revealing himself as a Venusian by uncovering his third eye. Haley says that the colonists will be Venusians, and laughs at Ross, also implying that he will kill him.

Appearances

 * The Twilight Zone, s02e28, "Will the Real Martian Please Stand Up?" (1961)