All characters belong to their respective creators, not me, this story may not be distributed on a profit-making basis.
Five Parental Nightmares Xander Never Had
(a 100-word Drabble in five acts)
"It's very simple," said Andrew. "Due to a mishap with a time machine, I am your father, Xander."
"There's a reason we called it the Scooby Gang," said Willow. "Once we knew..."
"I'll be a son of a bitch!"
"'Randson acruarry," growled Scrappy-Doo.
"It's very simple," said Giles. "Due to a mishap with a sex change ray, I am your mother, Xander."
"I'm Hitler's clone?" gasped Xander.
"You were." The Israeli assassins opened fire.
"It's very simple," said the President. "Due to a mishap with a condom, I am your father, Xander."
Crossover with Back to the Future, Scooby-Doo, Rocky Horror Show, The Boys From Brazil, the Presidency of your choice.
This was originally posted as a chapter in the Round Robin story Daddy's Coming to Visit Mommy's Come Calling on the Twisting the Hellmouth archive but apparently the original poster felt that Scrappy Doo, Hitler, and the President of your choice aren't evil enough to qualify under the terms of the original challenge...