Twilight Sparkle is in Golden Oaks Library, hoping to get away from the hardcore partying on the night of the Summer Sun Festival. She goes downstairs, fumbling in the dark as her horn isn't casting much light.
Also, Pinkie Pie is bouncing after her.
Pinkie: "So did you like the hot sauce prank? I can make it hotter if you'd like! Or get you vodka! You look like a vodka drinker!"
Twilight: *sighs* "No! I'm trying to save Equestria!" She glares at Pinkie as she trots on down "And maybe if you let me, I could-!"
She bumped into a stone statue, and looked up... Into a face.
Twilight: !!! "BWAH?!" She stumbled back in fright. Pinkie Pie found the light switch, and the face was revealed: As was the body it was connected to, all stone.
Pinkie: "Oh hey! A statue! Neat!"
Twilight: "Wha...?"
It was a statue of a human male, in his twenties, dressed in armor with the sigil of Nightmare Moon across his breastplate and strange feathered "wings" on his back. He had a sword at his side and a helmet sitting by him. He was kneeling, his chin on his fist as he sat and contemplated whatever was in front of him.
Pinkie: "What's it a statue of? Is it a flying monkey? Where's his fez?!"
Twilight: "N-No! This is a statue of Prince Andrew Shepherd, the Dark Prince! He was the adoptive son of Princess Luna, and fought beside her and Princess Celestia against Sombra. He was apparently from another world, but Luna found him and raised him as her own."
Pinkie: "Ooohh... Nifty! What happened to him? Is he stone? Did he get stoned?" giggles
Twilight: huffs "He apparently sided with his mother when she became Nightmare Moon. After her defeat though, he vanished." *She gazed up into the stone eyes* "Why would somepony make a statue of him though? When he was Nightmare Moon's Dark Knight?"
Pinkie: "I dunno..." She pokes him several times "Huh! He has pretty eyes! Is that why you're staring so hard?"
Twilight: flush "No! And that's not important!"
Pinkie: grins "Well I think he likes you, Twilight!"
Twilight: "What? Why?" groans "Wait, don't tell me."
Pinkie: "Because he's-!"
Twilight and Pinkie: "Rock hard."
Pinkie giggles and rolls around, as Twilight rolls her eyes.
Twilight: "Ugh, you're just impossible!" *She stormed off, Pinkie bouncing after her* "We have more important things to worry about!"
And indeed, they soon did! As Nightmare Moon returned! Twilight galloped back to the library, trying to find the key to the Elements of Harmony while five annoying ponies kept distracting her.
Twilight: "Ugh! Look! I need to find out where the Elements of Harmony are! And I need to do it alone! It's too dangerous!"
Dash: "Well too bad, because you're not going alone!"
Twilight: "Look, I don't need anypony's help!"
Pinkie: "Ooh! Ooh! Not even his help?" Points behind her!
Twlight turns around. Brushing off some stone flakes from his body, the fully rejuvenated Dark Prince Shepherd looks up at all six mares and one dragon.
Shepherd: "... Hey. Funny question, but-what year is it?"
Mares and Spike: "AAAAAAAAAAAAAAHHHHHHHHHHHH!"
Shepherd: "AAAAAAAAAAAAAHHHHHHHHHHHH!!!"
- - -
Different take on a Human in Equestria story: Princess Luna had an adopted human son, who became a Knight. When she turned into Nightmare Moon, he sided with her and then was frozen in stone for a thousand years. Then, he gets released and has to adjust to the modern world of Equestria.
I'm just using Shepherd as a stand in, it could work for any human OC. Or Flash Sentry.