Note:  This cheat is also known as E.T.

Level Password 

2 Up, Up, A, Down, Down, B, R, L 
3 Left, Up, Right, Down, L, A, R, B 
4 A, Left, B, Right, L, Up, R, Down 
5 L, R, R, L, A, Up, B, Left 
6 L, Left, R, Right, A, A, B, A 
7 B, R, B, L, A, Up, B, Up 
8 Up, Up, A, Down, Down, Left, A, B 
9 Right, B, B, Left, Up, R, R, L 
10 Left, Left, A, L, Right, Right, B, R 

Gameshark codes

(m)
E8FAD364  BC345C48  73FCAC9E  F8816305

Ar button level 2
52590BF0  80B43CF8

Ar button level 3
8E2A6D94  9E131E34

Ar button level 4
54F509A6  050DF553

Ar button level 5
D8031716  871BE359

Ar button level 6
31EF5FF0  DF787D36

Ar button level 7
D15EE6A3  76155609

Ar button level 8
72ED58A6  43C8CD70

Ar button level 9
C9CDA9E5  5C63BA6C

Ar button level 10
CE62ED1F  05696C14

Ar button credits
CDF4F623  DE00A931