10 More Changes That Star Trek Hoped You Wouldn't Notice

In the first episode of The Next Generation, Riker was extremely impressed by the holodeck technology aboard the Enterprise-D. He reacted as if he had never seen a more realistic virtual environment. However, in the Animated Series episode The Practical Joker, we saw that similar tech already existed a century prior.

In The Practical Joker, the Enterprise's computer was possessed by an alien prankster, who trapped Uhura, Sulu, and McCoy in the ship's rec room. In previous episodes, rec rooms were simply places of the ship where crew members could hang out and play games, but the rec room in The Practical Joker was able to generate fully immersive simulated worlds, just like a holodeck. We saw a forest simulation, a snowy blizzard, a beach, and a maze, complete with authentic weather conditions.

It's not clear how rec rooms like this were different from holodecks. Perhaps rec rooms were only able to generate environments, with no NPCs or storylines. While the three officers were trapped in the blizzard, Uhura explained, 'Look, this is still a room, no matter how it appears. If we can travel long enough in one direction, we're bound to reach a wall, then we can feel our way to an exit.' This didn't seem to be the case with the Enterprise-D's holodecks, so perhaps they were special for creating truly infinite worlds.