(Crossover with Stagate SG-1; spoilers and a little AU for Stargate S7)
Kenny's looking for a place to hide out, scoping out an isolated house when he sees the occupant, a grey-haired guy wearing sunglasses and an Air Force uniform, load some bags into a pickup truck and drive off. It looks like he's going to be gone at least a couple of days. There isn't an easy entrance for an adult, but someone Kenny's size can always find a way in. This time it's through a cellar window just right for a kid.
There's nobody there, just an empty house and a blinking light on the answering machine. Kenny presses "play," and a voice says "This is Siler calling for the General. Colonel, your cell phone is off. Sorry, the test flight schedule's been pushed forward, the General needs you back here for the next couple of days. Authentication Alpha Alpha Bravo Four Five. Please call in for further instructions when you get this message."
"Okay," thinks Kenny, closing the blinds and checking out the rest of the house. There's no sign of any other residents, there's food in the fridge, and a Playstation and widescreen TV. He ought to be all right overnight, in the morning he can loot the place, get as much as he can carry before heading out.
Kenny helps himself to pizza and a bunch of other stuff he's surprised to find in an adult's fridge (whoever heard of a grown-up liking Jello?), then watches TV for a couple of hours before hitting the sack. In the morning he feels like hell; maybe it's the strange bed, or too much pizza, but he's had more nightmares in a night than he usually has in a month. A lot of them seem to be weird sci-fi stuff, grey aliens that look like ET, weird rooms with flashing lights, paralysis as he floats in the air.
He's eating breakfast when he hears a thud outside, and sees a paper-boy riding off. He waits a couple of minutes, then goes out to fetch a bundle that includes two papers, TV guide, and a copy of Astronomy Today. Nothing to interest Kenny, but he's glancing through anyway when he gets a paper cut... which doesn't heal.
It's decades since Kenny's seen his own blood for more than a few seconds, and it frightens him. He waits to see the sparks as it closes. There's nothing. After he's sucked it for a while it stops bleeding, but the cut's still there. Kenny can't figure it out, and eventually he goes to the bathroom, finds a razor blade, and makes another small cut. This time, as before, it just bleeds. He doesn't want to risk any more experiments, so he finds a couple of Band-Aids and slaps them on, searches the house for valuables and finds a couple of hundred dollars, some games and DVDs, a couple of good watches, and a camera, all he can fit into his shoulder bag, then heads out. If there's something wrong with his Quickening he wants to be somewhere safe, there's no way he's going to risk staying here. The Colonel guy could come back, and Kenny might get hurt if he tries to fight him.
Three days later Kenny still isn't healing, and he's pretty sure his Quickening isn't working at all. He's on the move, sleeping wherever he can break in. He can't even fence the things he steals, there doesn't seem to be anyone around that wants to do business with a kid, so he keeps the cream of the crop and ditches the rest.
Four days, and Kenny has his first wet dream. He knows about sex in theory, but until now that's been all. Hair's starting to grow in his armpits and on his body, and his clothes have started to feel a little tight. He's aging, and terrified. How long is he going to live without the quickening? Eighty years? Fifty? Twenty? He could be run down by a truck and he'd die, no recovering in the morgue.
A week, and the growth spurt seems to have stopped. He judges he's physically about twelve or thirteen, maybe a little more. If his immortality is gone for good what will he do with the rest of his life? He doesn't have any useful skills, and mostly his education is a few hundred years out of date. He can fight, but without the Quickening he doesn't want to risk it.
Ten days, and Kenny is walking down the street, pretending to be just another boy playing hookey, when he sees the headhunter coming towards him. Kenny's too terrified to run; he just keeps going, praying that he won't be recognized. There's no buzz, nothing at all, and the guy doesn't even glance at him as he passes. The Quickening has definitely gone.
Two weeks, and Kenny is breaking into yet another house when he feels dizzy. It isn't the Quickening, just some sort of sickness. He turns to get away, makes it all of four or five steps, then collapses.
Kenny wakes in a hospital bed. He's aching all over, and there must be a dozen tubes going into his body. He manages to focus for a second, and sees someone in surgical greens talking to a cop. "...I don't care how many houses he's robbed, he can't be questioned."
"Did you check out that pig-sticker he was carrying?" asks the cop.
"I saw it," says the doctor. "But this kid's too ill to move, let alone fight."
"Then you'd better call me as soon as he's better."
"That won't be..." says the doctor, then notices that Kenny's eyes are open, and says "Can you hear me, sonny?"
Kenny tries to say something, all that comes out is a moan.
"That's all right," says the doctor, injecting something into his arm. "Don't try to talk. Save your strength."
Kenny's falling asleep again when he hears the cop say "How long has he got?" He's unconscious before there's a reply.
Kenny never regains consciousness. Three days later he's dead, victim of a condition the coroner's report describes as "cellular breakdown." The CDC wastes months looking for signs of Ebola or some similar infection, but finds nothing. Eventually he's cremated.
Several hundred thousand light years away the real Kenny is beginning to wish that he hadn't killed the alien. He's tried to find food aboard the ship, but there's nothing that looks even vaguely edible, apart from the body, and he's getting nowhere with the controls. He's starving to death, but unable to die, when Loki's spaceship finally leaves the local cluster of galaxies behind a few months later. The Asgard make good ships, and it will be centuries before the hull fails or the engines die and Kenny is finally killed. He'll never know that he briefly had a clone.
Since I posted the first story I've learned that Myles Ferguson, who played Kenny, died in 2000 aged 19. I think that it's a tribute to his acting that this character is so unlikeable, and hope that nobody will feel that these stories are disrespectful to his memory.