Today it was revealed that Super Smash Brothers Brawl will come available with Virtual Console demos. Many games such as Super Mario Brothers, Ice Climbers, Legend of Zelda, Star Fox 64, have already been confirmed.
The demos work by allowing you to play the game for a set time limit. Once time runs out, you see the following message, informing you that time has run out:
Though some games have pre-loaded saves in them, so you can start from different places. This works in games like Super Metroid, which was also confirmed.
What is unconfirmed is if this feature will expand through downloadable demos or is limited by the content that comes on the disc. And if it is limited, chances are Nintendo will make demos available in the future on the Wii Shop Channel. Also, every demo featured in Brawl, is available for purchase on the Wii Shop Channel. Most likely, these demos will act as unlockables throughout the game, but I could be wrong.
Not all of the titles that make use of this feature is yet known, though chances are each game shown will feature a character who is playable in Brawl.