One level will take place in Princess Peach's Castle.We know that part of the game's story will have to do with Mario and. co making their way back to the Mushroom Kingdom after getting thrown out by Bowser. By the time you clear the seventh world, you'll be closer to familiar territory (and from there you'll probably go through a few levels evocative of the previous home console installment, with the same music, scenery, and all. Peach's Castle, now overrun with Bowser's minions, will serve as a transition to the final world (like the Mysterious Sunken Ship in Super Mario World). After Mario and co. storm their way through the castle, they'll find Bowser on his airship with Peach, about to take off to his lair. The heroes will grab on to it before it leaves, and after a quick auto-scrolling airship level, you'll begin World 8.
There will be more hidden in this game than has been revealed so far.Super Mario World had a lot of secrets in it, both revealed in the manual but hidden in-game, like Star Road and the colored yoshis, and super-secret, like the Top Secret Area and the Special World. I think in this game, Nintendo will return to form and have secret powerups and stages that aren't advertise as selling points for once. Then, when people discover them and spread the info virally, it will build more hype than any advertising campaign could. Some secrets that could be anticipated:
Nabbit is a Rabbid
The Secret Toad House......belongs to Monita. She's been following Nintendo characters for years, and analyzing them on their adventures allowed her to create Nintendo Land. The Secret Toad House is her current home base, explaining the billboard full of data on what you've done.
Nabbit is a Toad.Based on this piece of fanart, it's entirely possible he is not a rabbit at all, and his real face is hidden behind his bandanna.