I don't consider this much of a spoiler myself, since most people probably wouldn't find it without knowing. Others might see it differently though, so reader beware!!1!eleven.
The official strategy guide for Super Mario Galaxy reveals a cool tip allowing you to play as Luigi, but only after you've thoroughly beaten the game using Mario.
Firstly you need to have done all the purple coin missions and collected all 120 stars.
Luigi is said to handle a little differently to Mario, he can jump higher and run faster, but is harder to stop (like in the Lost Levels).
3,039 news items
NBA Playgrounds new content teaser
Switch must wait again
A day with Pokemon GO Down Under
Splatoon's Last Ever Splatfest is Coming
And It's Sister vs. Sister
Nintendo President Satoru Iwata Passes Away at 55
Rest In Peace
Nintendo has detailed the return of its World Championship
Do you have what it takes?
Disney Infinity 3.0 Edition Officially Revealed
The Force is strong with this one...
Rumor: Disney Infinity 3.0 Leaked Early
Straight from a Galaxy Far, Far Away...
Mario Kart 8 DLC Pack 2...OH YEAAAAH!
Nintendo should do this more.
Wii's World is not officially affiliated with Nintendo! (but they wish we were).