Change from samus to different characters:
Make a new file. Hold down Z and R during the introduction while entering these codes.
Kreana-L, up C,down C,right C, up C, down C, L, D pad up,D pad down,D pad right,D pad up, D pad down, right C,D pad left,
Left C,D pad right,up,left,right,down.
Starship pilot-Up,Down,Left,Right,Right,Left,Down,Up,Up,
Down
Kraid-L,L,B,X,Y,B,X,Y,A,A,D pad Down,
D pad up,D pad down,D pad up,D pad left,Left C,L,L,B,Y,X,B,L,L,A,A,A,A,Y,X,B,L,L,Left C,D pad left,D pad up,D pad down,A,A,Y,X,B,Y,X,B,L,L,A,B,X,Y.