Starman and K-PAX are both about curious benevolent ET travelers. In Starman, the ET makes a copy of a former human to use it as his earth-suit. In K-PAX, the ET travels to earth in the form of photonic data transmission. He has temporarily taken over the body of a previously traumatized human. Upon his departure for return trip, it becomes evident that the body who was temporarily under the control of K-PAX has become catatonic.
In contrast, Invasion_of_the_Body_Snatchers is about an ET consciousness that copies a person in order to have an earth-suit, thus causing the original to die.
https://en.wikipedia.org/wiki/Invasion_of_the_Body_Snatchers_(1978_film)#Plot
THE-THING absorbs and copies the life forms of the worlds that it visits.
