(To clear up any perceptions, NO, the Mysterious Stranger is NOT related to the Fallout franchise in any way, shape and form!!!)

Sunset Shimmer had just finished her classes for the week, and was going to hang out with her Canterlot High friends for the weekend, including the new transfer student; Twilight Sparkle of Crystal Prep...

But...
Family emergencies pull the six girls to head home for the weekend, leaving Sunset alone for the weekend, feeling somewhat disappointed that she'll be all alone...

Feeling the need, she went out for a stroll in an unusually strong storm that appeared out of nowhere, thinking it might help wash away the feeling of being alone.
She wasn't exactly expecting to shelter a poor, homeless man from the storm's vicious rain and winds. The moment she made contact, Sunset noticed something unusual about the presence of the man, something obviously not human from the vibe she's getting, but something not of Equestrian origin as well...

She couldn't describe in detail the aura the poor man was giving off, but if the feeling had to be described...

Sunset Shimmer would say that the man felt;

(My first one-shot, I do not own the picture, I only used it to fit the story, credit belongs to its original artist creator...)