It turns out they were just using a second Wii console off camera to play the 'backup' disc.
Crunchgear posted a YouTube video (which has since been removed) where a gamer claimed he had already hacked the Wii to enable it to play burned copies of game discs. As it turns out, the video was completely fake. Apparently he had a second Wii console off camera. By inserting the real Rayman game disc into the second Wii at the same time as he inserted his fake disc into the Wii on camera (which was not even hooked up to the TV) he was able to make it look like the backup disc was playing the game.
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