Starmen are an alien race which are common for using a psychic power called PSI. They are important in the Mother series and they are the minions of Giygas.
Starmen are humanoids, wearing platinum suits. Their heads are directly connected to their shoulders with no discernible neck and they have a visor, no digits on their hands and shoe-like feet. They also have four black buttons on the left side of their chest.
Starmen are half organic, half synthetic. They are synthetic because in Mother 2/Earthbound, Starmen use katakana script which is a common way to donate robotic sounding speech. The English version lacking this gives them "whirrs", "beeps" and "clicks" which indicates that they are robotic. But they are also organic as they cannot be harmed by the Rust Promoter, which only damages robots.
Starman Junior - The Starman Junior is the weakest out of all the Starmen. It has pink skin in Mother/Earthbound Zero, but looks like a normal Starman in Mother 2.
Blue Starman - The Blue Starman is an upgrade version of a Starman which uses all forms of PK Beam, except Omega PK Beam. It has a tint blue.
Last Starman - The Last Starman is the most powerful out of all the Starmen in Mother. It has low HP, high defense and access to all PSI attacks, including PK Beam. It has gold skin.
Starman Super - The Starman Super uses PSI Shield and PSI Healing which revives defeated enemies. They all disappear, after a Starman Deluxe is defeated. Its appearance is similar to the Last Starman's.
Starman Deluxe - The Starman Deluxe can use PSI Shield, PSI Starstorm, fire a beam and summon a Starman or a Starman Super. It has silver skin, spikes on its head and shoulders, and red buttons on its chest.
Ghost of Starman - The Ghost of Starman is powerful Starman which uses PSI Starstorm. It has black skin and pink buttons on its chest.
Final Starman - The Final Starman is the most powerful in Earthbound. It can use PSI Shield, Brainshock, PSI Healing and PSI Starstorm. Rendering PSI attacks against it are useless until its shield is removed. It looks exactly like a Starman Deluxe, except it has gold skin instead of silver.