Star Trek: 10 Weirdest Holodeck Episodes

In this case, a difference that makes no difference is no difference at all, as William James once said. Or, in other words, if it quacks like a duck on the holodeck, it probably quacked like a duck in the Rec Room. Three members aboard an animated Enterprise found that out the hard way in The Practical Joker. There weren't any ducks, but we did see some simulated seagulls.

Kirk is a jerk and Scotty is left pie-faced when the Enterprise computer starts to take on a mind of its own after its circuits are affected by "highly charged subatomic particles." At first pulling relatively harmless pranks to amuse itself, the computer ups the ante by trapping Doctor McCoy, Sulu, and Uhura in the Rec Room — the 23rd century equivalent of a holodeck. The environment switches from woodland to arctic blizzard to enormous hedge maze before two crewmembers manage to pry the doors open from the outside.

14 years before the events of The Practical Joker, and 105 years after Unexpected, the USS Discovery had its own fairly realistic holographic simulation room, used for target practice in the episode Lethe. Gene Roddenberry had wanted to include a version of The Practical Joker's Rec Room in the third season of Star Trek: The Original Series, but without even holographic dollars left in the budget, this would have to wait until Encounter At Farpoint. In all that time, however, they still hadn't worked out the kinks!