lunabee34 says: "Tell me about the episode (or book chapter) that never appeared in one of your fandoms but should have."
Star Trek TNG: "The Price" is such a god-awful episode that when it leaves those two Ferengi in their shuttlecraft stranded in the Delta Quadrant and doesn't bother to tell us what became of them, that's not even the worst of its crimes. (The worst of its crimes is probably what Crusher and Troi wear to do aerobics.) Anyhow, yes, the Ferengi were acting like jerks, but they didn't deserve to die the kind of death that you'd die stranded in a shuttlecraft 30,000 light-years from home. I think either they should reappear as part of the Borg collective, or the Voyager crew should find them.
Due South: More Ray&Ray. Doesn't everyone want more Ray&Ray? Make RayK go to meet a new informant and discover that it's the Bookman.
The Princess Bride 2: the story of how Buttercup wound up being the Dread Pirate Roberts.