Everything But The Kitchen Sink

Discord discovers that Princess Celestia developed a new hobby while he was trapped in stone. Unfortunately, that hobby was fanfiction.

Successfully 'reformed', Discord is free to wander the Canterlot Palace.
He and Luna find a specific room that Celestia has warned all away from.

So, naturally, they find Celestia's fanfiction.
And she's been writing shipping for about the past thousand years or so.