What if, Wii U games read your save files for other games like in Super Mario Galaxy 3 if you have Zelda HD you get the ability to have Luigi dress like Link, or get a download of a world that is made up of Zelda themed levels. And in Zelda HD you could download a special mario themed dungeon, kinda like in Link's Awakening's dungeons but with koopas as well.

Don't we have enough DLC threads? It would be pointless to have to download something like that anyway, just have it automatically unlock when it notices the save file, as most games that have that feature do.

What's so wrong with paid DLC anyway? The people who made the game get more muniez for optional content that you're in no way obliged to purchase. Unless it's one of the WiiWare FF games.

The problem with having it on the disc is it would be incompatible with future games so if the Zelda is launched a year later Nintendo would have to put the feature in and not be able to test it without having the disc, and if the games is cancelled then the space of a world on Mario Galaxy 3 is wasted.

My idea is slightly different. On disc/cart DLC is unlocked when you download a specific Virtual Console game that isn't going to get that many sales to help boost that game's sales.

This way you're still paying for DLC but you also get a Virtual Console game in addition to the DLC. Okay, so many people wouldn't be happy about downloading Donkey Kong Jr. Maths to unlock content for Donkey Kong 3D Land but I think this is something companies should do in future.

That would be cool, but I'd like to get bonus content for retail games as well.

Well you unlock Rosalina in Mario Kart Wii if you have a Super Mario Galaxy save file so there is precedence with your idea.