This is inspired by Bad Seed 72's fanfiction "What Hath Joined Together". But the events in the story are not canon to the story's universe.
The story shows Captain Iron Hoof, the Captain of the Royal Guard, dreaming of his wedding to Princess Twilight Sparkle a little way in to the future of "W.H.J.T."'s timeline.
Meanwhile, Twilight and Flash decide to take a detour while flying home from Pinkie Pie's latest party.