Meowth's Party (lost Nintendo GameCube tech demo; 2000)
Meowth's Party is a real-time tech demo that was shown at Nintendo Spaceworld 2000. It was created by the same team who worked on Pokemon Stadium to show off the GameCube's graphical capabilities and features Meowth singing and dancing on the stage, where he soon gains a crowd of many Pokemon to watch his concert.
According to Nintendo, the team took the end sequence used in episodes 117-141 of the Pokemon anime and made an interactive tech demo out of it. The demo ran off of the GameCube's hardware to demonstrate its capabilities, running in high resolution and at 60 frames per second. While it wasn't as graphically impressive as some of the other demos and even had frame issues at certain points, the models present in the game were very smoothly rendered and ran independently of each other. It also displayed a fairly impressive lighting system.
While there was speculation at the time that the concept would have been made into its own game, this never happened, possibly because GameFreak felt that the concept didn't have enough weight for an entire game. However, it was ultimately implemented into the GameCube game Pokemon Channel for the ending of the in-game cartoon Pichu Bros. in Party Panic, where Meowth would sing the same song as in the anime as well as perform random actions to his crowd. The demo has not been used for anything since.
While a version of the demo was put into Pokemon Channel, the original tech demo has yet to surface in any form and, apart from the ability to move the camera, it's unknown what extent of interactivity the demo had.