Video Games: Understanding Super Mario Galaxy

Unlock Luigi!

Here's how to get Luigi. First, get all 120 Stars in the game. Second, return to Rosalina (on the Comet Observatory) and
ask to fight Bowser one last time. Third, defeat him and let
the credits roll. Last, wait for a message that tells you Luigi
is a playable character.


Unlock 121 Stars!

There's actually 121 Stars in the game, not 120. To get the
121st, unlock Luigi and then use him to beat the entire game.
Thereafter, a new galaxy will unlock. Complete it to get the
121st Star.


Second Player Capability

If you have two Wii controllers, a friend can play along with you.
While there won't be a second player on-screen, there will be a
second cursor for collecting Coins, Star Bits, e.t.c.. The cursor
can also be used to partially control Mario's jumps.