I can't decide between
Your challenge is to write crossover fanfiction combining Murphy Brown and South Park. The story should use terrorism as a plot device!
and
Your challenge is to write crossover fanfiction combining Final Fantasy 8 and Samurai Pizza Cats. The story should use legalizing gay marriage as a plot device!
or possibly
Your challenge is to write crossover fanfiction combining the National Hockey League and Romeo & Juliet. The story should use oral sex as a plot device!