To get Mario:
     You have Yoshi and you go were all the doors with letters on them
L  (Luigi), M(Mario) & W (Wario). Then there is a door without it just
in  front of you. Go to the game room, to get Mario you have to have 8
stars. Go to the room with the #8 on it and there will be a Mario pic,
go into the pic and beat the level and you have Mario.

To get Luigi:
     Go  to  the  courtyard  and you'll see a Boo (ghost). Go into the
door  that the boo went in and you'll either see a big Boo or just see
smaller ones. If you see smaller ones you get the red coins. You and a
star  will  appear  and then you get the star. Go out the door then go
through  the doors again and you'll see a big Boo on either side. Kill
the  big  one  and  go  into the cage. Its a level so you do the first
level  then there are stairs. Go up the stairs after getting the star,
go  to  the right then go to the other right door after turning right.
Get  the ! box and get to the top (you have to have Mario) and press R
to  land. You'll see a Luigi pic, go into it to beat the level and get
Luigi!

To get Wario:
     Go  to  the  top floor with Luigi and go to the mirror room. Then
eat  the  flower.  Go  to  the  Wario picture where the guy is wearing
yellow, go into the pic!