In Super Mario 3D Land for the 3DS, in one of the levels of World 6, if you have a tanooki suit and the right amount of momentum, you can fly over the level and finish it without even having to do the level.
Also, there is some confusion about whether or not the Mario Bros are twins. In the Paper Mario game on the Wii, during one of the first cutscenes, as Count Bleck attacks Mario, Luigi yells "Big Bro!", indicating that Mario is older than Luigi. However, in the original Yoshi's Island on the SNES, at the very end, it refers to the brothers as "twins". So, confusion is there