I love stories where Aliens Made Them Do It.  I am looking for a story where Kirk and Spock are kidnapped by a slaver who is under hire from a planetary leader who has a fixation on the great Captain James Kirk and his first officer Spock.  The leader wants the slaver to bring Kirk and Spock to his planet where they are suppose to put on a sex show for him.  The slaver, after getting them on his ship, tells them this and says if they do not "perform" they will be sold to the Klingons or the Romulans.  He tells them they have three days of traveling time to "practice" before they arrive at the planet.  Oh, and there is no way for them to escape the slavers ship.  So, much angst ensues while Kirk and Spock are faced with whether or not they should go ahead and "practice".  They are, of course, eventually rescued (after the practicing) and taken back to the Enterprise.

Bonus points if neither Kirk nor Spock ever thought of each other in a romantic way before.