A story (a 'real person fic') in which Kirk, Spock, and McCoy are somehow accidentally beamed to the (then-) present-day set of Star Trek, filming in progress, and must pretend to be their counterparts (Shatner, Nimoy, and Kelley) until they can be rescued. Great literature it's not (and the more general premise of Trek characters traveling to present-day Earth had been done six months earlier in the TOS episode "Assignment: Earth" and a year before that in "Tomorrow is Yesterday", and travel to 1930 in "The City on the Edge of Forever"), but it's a serviceable bit of comedy. This story would have a number of sequels by different authors.