I think i found this one out myself, but it would be nice if somebody could confirm it:
What i remember: a guy "playing dead" in a bodybag, so that he can go to another planet and fight an alien / aliens. I think the alien has a brown colour.
It resembles the one in this movie:
so yeah, is there a scene with bodybags in "the last starfighter"?
if not: any idea which movie i refer to?