Five.
"It's very simple," said Andrew. "Due to a mishap with a time machine,
I am your father, Xander."
"Noooooooooooooooo!"
Four
"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.
Three
"It's very simple," said Giles. "Due to a mishap with a sex change ray,
I am your mother, Xander."
"Nooooooooooooooooooooo!"
Two
"I'm Hitler's clone?" gasped Xander.
"You were." The Israeli assassins opened fire.
One
"It's very simple," said the President. "Due to a mishap with a condom,
I am your father, Xander."
"Nooooooooooooooooooooooooooooooooooooooo!!!!!"
End
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 Twisting the Hellmouth 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...