Has anybody here ever played diablo 2? There were tons of optional dungeons in that game. You'd be walking in the desert killing giant beetles and tiger people and you'd see a hatch that you could climb into and it would be a whole optional level (in this case probably a tomb or crypt). In the last part of the game, which was, for the most part, a giant battlefield, you would find option portals to different versions/parts/types/names for hell. You'd see a portal and it would be called abaddon, and you'd go in and it would be a whole different setting (a path atop an ocean of lava or an evil hell palace)with completely different enemies. This was really exciting, and I hope they incorporate something like this into skyward sword. I doubt it because they said the gameplay would be very linear, but still...
Another cool dungeon thing from that game would be: if you killed some of the minor bosses a bunch of times, they'd each eventually drop a key or something, you could fuse all the keys to make a portal into an awesome side dungeon with an awesome renamed and recoloured version of a game boss, then you could kill them to get portals to another place... I forget exactly how it goes, but to sum it up, it was an extremely difficult sidequest done after game completion in which you would fight gradually awesomer and more difficult bosses in different side dungeons with strong enemies. It was actually included in an update, which gives me another idea...
Maybe nintendo could update our game or have a channel for it so would could do maybe an extra side dungeon a month, maybe like Mario Kart? That would be really neat, and you could gain rupees or something upon completion. Seeing as the dungeons in the actual game don't seem to be in the classic style, these released dungeons could be, and it would be heavily appreciated. Again, I doubt it'll happen, but that would be really neat. The dungeons would not need to be stumble-upon, and they could retain the linear gameplay that they promised.