If the concept of mood slime existed in any movie other than 1989’s Ghostbusters II, it would be considered one of science fiction's most clever and compact conceits. If Douglas Adams had lifted the movie’s basic plot structure it would be quoted on bumper stickers. And yet the world-building notion that ectoplasm — the residue left by ghosts — can be weaponized for good or ill by our emotions simply isn’t treated with the reverence it should be, nor are the several other innovations introduced in Ghostbusters II.
