WiiConnect24 (partially found video game demos; 2006-2013)
WiiConnect24 was a service that offered online experiences to users of Nintendo's Wii console, which launched on November 19, 2006, and ended on June 28, 2013. Some of the services offered included the "Everybody Votes Channel," Mii avatar sending functionality, Wii messages between friends, and the Nintendo Channel, a video channel featuring trailers, advertisements, and most importantly, demos for upcoming and released DS games.
However, many of these demos have been lost due to the unique way the DS downloads and stores demos. It deletes them after a set amount of time or when the system is turned off. (the demo is stored in temporary memory) Therefore, some games cannot be completed on both Wii and DS because they require data from demos or other WiiConnect24 services. For example, Metroid Prime Trilogy (Wii) no longer has the ability to share Green Credits, which stops you from unlocking all bonuses, and Kingdom Hearts Re: Coded (DS) requires WiiConnect24 data to complete the Avatar Gallery and 100% complete the game.
Current Fan Efforts
While some demos have still not been recovered, many have been dumped online. Most of them are available in this Google Drive folder. No-Intro has known DS demos listed in their "Nintendo DS (Download Play)" dat file.
The current effort to recover WiiConnect24 services are spearheaded by the project RiiConnect24, which brings back Wii Mail services and the Forecast, News, and Everybody Votes Channel, along with DLC for Animal Crossing: City Folk.
There are also methods to cheat to receive the 100% completion of Kingdom Hearts Re: Coded and Metroid Prime Trilogy.
1. "Update- wiiconnect24 has ended," video by scatlink sean; Published Jul 1, 2014; accessed Dec. 20, 2016
2. "RiiConnect24," website by the RiiConnect24 development team. (https://rc24.xyz/)