Harry Potter Gives You a False Expectation of Train Compartments (Bellarke)
Clarke finds out her boyfriend Fisher is actually named Finn (and is engaged) two days before they were supposed to go across the country on a train to start a life in California. Bellamy had some awesome plans, but they got cancelled, leaving him with nothing to do. A crazy and out of left field proposal from Clarke to Bellamy changes their lives forever.
or
a really long one-shot based off the lyrics from Anna Kendrick's 'Cups' set to a modern Bellarke AU.