The difference between reality and fiction? Fiction has to make sense.

Clancy here expresses an idea evoked in similar statements made by others, all derived from the orignial made by Lord Byron: Lord Byron: Truth is always strange; stranger than fiction. Mark Twain: Truth is stranger than fiction, but it is because fiction is obliged to stick to possibilities, truth isn't. G. K. Chesterton: Truth must necessarily be stranger than fiction, for fiction is the creation of the human mind and therefore congenial to it. Leo Rosten: Truth is stranger than fiction; fiction has to make sense. (attributed)