Fifty Shades of Fanon

This is a collection for the Fifty Shades of...Challenge on HPFC. (It doesn't have anything to do with Fifty Shades of Grey. I don't read that series.) Multiple pairs. First few pairings are Katie/Oliver, and the latest pairing is Marcus/Katie, my new favorite pairing. They try to figure out where they stand the night before they compete for the Quidditch House Cup.