Celestia has been having recurring dreams; dreams that she wishes would go away. But they only increase in their frequency. One night, she gives in and visits that statue in the royal garden. The statue that haunts her sleep. The statue of her love.
Princess Celestia asks Twilight Sparkle to accompany her on a picnic with plans to seduce her younger protege. Celestia X Twilight (nothing too crazy tho it's a T rating for gosh sakes) ;)
Princess Luna sees somepony's dream, one of a more intimate variety. Normally she would just move on without a second thought, but there's something different about this one.