This question is about the book by Stephen King, not about the movie. In the book, and near the end, it is revealed that "Mr. Gray" was somehow a figment of Jonesy's imagination. However, and maybe because King doesn't specialize in writing SF (though I love his horror stories), the explanation seems confusing to me.
- To what extent was Mr. Gray a product of Jonesy's imagination? Was there any kind of infection at all? Did he have any "byrus" inside at all? King seems to imply it was a complete hallucination, but in that case, why was the alien "learning" to be human? Why did he have an "imperative to seed", if he didn't exist at all?
- Were all the "grayboys" a collective hallucination of the main characters and their antagonists from the army?
- Who were the actual aliens? I think King actually comes close to answering this with the non-sentient byrus (the fungus) and the byrum (the "shit weasels"), but it still doesn't make sense... If the grayboys don't truly exist, who built the spaceship? Or was the spaceship itself an hallucination?
Maybe it just doesn't add up, or maybe there is something I missed in the book :)