Enter the level as Mario or Luigi. Go to Goomboss and he will talk to you for a second. Then, run around to the back of the Goomboss and kick him. (he wont get hurt) He will then make a Goomba behind him. Run to his back again and punch the Goomba into Goomboss's back. Repeat twice. Then he will explode along with the Goombas. Then you will get Mario's door key again.
(The hey is wrong with you?) No, you cannot kill Luigi in Super Mario galaxy. (He's too precious)
eat goombas with Yoshi and throw then at the gayass goomboss
The trick is kill Fake Luigi first, and it will make it about 100% easier. If you kill Fake Mario first, then Fake Luigi will give him a 1-Up Mushroom. Fake Mario does not have any 1-Up Mushrooms.
koopa troopas and luigi
By defeating him in battle.
Get 8 stars,go to the room with the number 8 on it,jump in the Mario painting,defeat Goomboss.
easy pals just kick him twice
Mario and Luigi are twins, but Mario is older.
luigi and Mario . luigi and Mario . lugi and Mario.
Yes its Luigi.
There is no official answer, honestly. All we know is they are Mario and Luigi's "evil counterparts." well Mario and luigi are cousins and waluigi and luigi are brothers Mario and Luigi are brothers... and I highly doubt that Wario and Waluigi are cousins with Mario and Luigi.
Mario and Luigi are from Italy