Wellsian Martians are a species of sentient alien beings in the in-universe book War of the Worlds and its film adaptations.
Description[]
Bearing little resemblance to any known breed of real-life Martians, the octopus-like Wellsian Martians were the brainchild of 19th-century English writer Herbert George Wells in his novel War of the Worlds, being his take on what inhabitants of the planet Mars might look like, as envisioned long before there was actual contact between Earth and the Red Planet.
These Martians were shown in the novel to use advanced technology to attempt to take over the Earth, due to their world being a dying, nigh-uninhabitable one. While on Earth, they made use of technology such as large walking machines called Tripods and Heat Rays, but ended up falling prey to Earthly germs against which they had no immunity, forcing them to retreat.

The Wellsian Martians in Mars and Beyond (1957).
Though another visualization of Wells's novel's event showed them as tall, ominous, greenish creatures, as seen on the left, the 1987 film adaption of War of the Worlds starring Mickey Mouse instead depicted the Martians as small, almost cute creatures with round blue noses, who get around on short, leg-like tentacles. They communicated in a language rendered in writing as a series of rather easily-interpreted pictograms.
Coincidentally, a species with a broadly similar biology and a strikingly similar history existed in a parallel world, calling themselves the Wellsians.
Behind the scenes[]
The Wellsian Martians appear in the 1957 TV special Mars and Beyond and in the 1987 story War of the Worlds; they are, of course, a Disneyfied reimagining of the original H. G. Wells Martians.
It is unclear if the Wellsian Martians as seen in Mickey's movies were achieved through some sort of special effects, or portrayed by actual Martians (which would mean that Wellsian Martians exist after a fashion in the Prime Universe, though their history and culture may not be that ascribed to them in the film).