Disclaimer: Every character (except the Dark Koopa Lord, another fan character of mine; no description is said in here) belongs to Nintendo. Also, take note that Koops' father, Koopley, will be introduced somewhere near the beginning.
"The day we found the young Koopa… Was the day we found out that he isn't truly a Koopa."—Koopa Koot, 11 years ago
When the young Koopa in his mother's arms was born, his mother, Koopuri, a Dark Koopa, with purple eyes and a blue-colored shell, had a look of doubt on her face. She said to her husband, Koomplex, a Koopa with blue eyes and a green shell, "I love my son as much as I love you. But I have to ask… How long do we have to keep our love a secret?"
"We must, and we shall, keep it a secret for the rest of our lives, or until we're caught by the Dark Koopas," Koomplex said as he looked at his wife, then at his newborn son. The child opened his eyes, revealing them to be a light blue-violet color. The father tickled his son's belly and continued, "But for our son, Kooper, that'll be a bit hard, considering his eyes are of both heritages."
As Koopuri placed Kooper onto the white twin-sized bed, she slipped on his small, blue shell. "Yes. I'm afraid of him more than our secret. After all, most Dark Koopas have taught their children how to distinguish a Koopa from their own kind."
Koomplex nodded. "You're right. We must be careful… For our son's sake."
For the next six years, the two made sure that Kooper stayed away from the other Dark Koopas, especially adults, whenever possible. Koomplex, a former teacher at an elementary school, started to home-school him when Kooper reached the ripe, preschool age of five. And Koopuri, at one point a botanist with a small medical background, taught Kooper about plants and animals, and demonstrated a few herbs and plants that help heal certain wounds and sicknesses.
Everything went well until year six, on Mother's Day, when a friend of Koopuri visited and found out about their secret. The friend, the gossip of the town, accidentally revealed it to every adult in the town, and word spread to the Dark Koopa Lord, whom sent his army to search the house. The leader of the army, General Koopley, ordered his right-hand soldier, a sixteen year-old green-shelled Paratroopa with an unknown name, to eliminate Koomplex. Shortly after he beheaded Kooper's father, Koopuri was sent to prison for life for having love affairs with a Koopa.
Almost immediately, Kooper was then banished and they left him in Koopa Village. Fortunately, ten minutes later, Kolorado, returning from a recent expedition, found him lying on the ground and took him in. A week later, after introducing Kooper to the village, Kolorado says he has to leave for another expedition, and left him with Koopa Koot, the mayor of the village.
Due to his wisdom, Koopa Koot figured out that Kooper was half Dark Koopa, but he ignored that fact and raised him as if he was his own grandson. "Kooper, because of your parents, the Dark Koopa army will attack us someday. I'm not sure when, but they will. And be on your toes when you talk to other Koopas. Most of them, like with Dark Koopas, can distinguish a regular Koopa from a Dark Koopa."
Kooper heeded his words, not only because he was the mayor, but also because he was wise. And four years later, as Koopa Koot predicted, the Dark Koopa army attacked the village. Fortunately, the PAF arrived not too long after. Also fortunate, Koopley retired from the army three years ago to fight off Hooktail, whom was a great threat to his (real) hometown, Petalburg.
The battle went on like any other that existed: bloody, violent, and horrible. But when all seemed lost for the PAF, Koopley's right-hand soldier suddenly went insane and destroyed almost half of the Dark Koopa army, but about a third of the other. Apparently, an ally and best friend of his was executed by a small group of Dark Koopas (whom were members of the Dark Koopa army and foes of the ally).
Two years later, the battles ended, as the PAF's new "secret weapon" finished off the Dark Koopa army in the forest outside the village. A week before his birthday (Day "Heart-Circle") and grateful for the protection of the village, twelve year-old Kooper asked the green-shelled Paratroopa for his name.
The Paratroopa answered before leaving, "Young Koopa, just call me… 'Sky Aerith'."
Five years later, hoping to find adventure after spending most of his life in Koopa Village, Kooper joined Mario on his quest to save Princess Peach from Bowser, who stole the Star Rod from Star Haven. Not too long after, a mailman from Toad Town, a familiar looking green-shelled Paratroopa named Parakarry, joined Mario as well.
Though even after Mario defeated Bowser and brought the Star Rod to its rightful place, Kooper still finds something about the mailman that bugs him.
Slightly cheesy ending, I know. TT;; So, anyway, yeah, the Paratroopa in Kooper's past is the same Paratroopa from Doopliss' past. (cough How convenient. cough) Especially when it mentions about Parakarry joining Mario.