This story is a sequel to Under the Starry Skies

After a recent humiliating experience involving too much chocolate mead and karaoke that was less than "family friendly," Fluttershy flees into the safety of the forest to escape the mess she's made. Wandering aimlessly for hours deep in thought, she comes to and realizes she has no idea where she's wandered, is incredibly thirsty, and very uncomfortable under the late summer sun. So, when she discovers a chilled pond with which to slake her thirst and cool down, she pays little heed to the strange green bush on the far side. That is, until it opens its eyes.

Creds to OminousBrony for cracking the whip, and tossing in ideas.
art by askheroichamburger of DeviantArt

A Spartan of the UNSC falls into Equestria and has various shenanigans in the land. First chapters revolve around how he meets the royalty, the mane six, and the new world in general.