Dark Rift

Unlock Sonork as playable character:
Go to the title screen and press the following button combination
when the "Start" message appears: L, R, C-Up, C-Down, C-Left, C-Right.

Unlock Demitron as playable character:
Go to the title screen and press the following button combination
when the "Start" message appears: A, B, R, L, C-Down, C-Up.

Unlock Demitron as opponent:
Go to the title screen and press the following button combination
when the "Start" message appears: Up, C-Left, R, Right, Down, B,
B, B, C-Up.

Watching the character endings
Go to the title screen and press the following button combination
when the "Start" message appears:

Zenmuron: Press Up, C-Left, R, Right, Down, L, L, C-Right.
Sonork: Press Up, C-Left, R, Right, Down, L, L, C-Up.
Scarlet: Press Up, C-Left, R, Right, Down, L, L, C-Left.
Niiki: Press Up, C-Left, R, Right, Down, R, R, A.
Morphix: Press Up, C-Left, R, Right, Down, R, R, B.
Gore: Press Up, C-Left, R, Right, Down, R, R, C-Down.
Eve: Press Up, C-Left, R, Right, Down, R, R, C-Right.
Demonica: Press Up, C-Left, R, Right, Down, R, R, C-Up.
Demitron: Press Up, C-Left, R, Right, Down, L, L, C-Down.
Aaron: Press Up, C-Left, R, Right, Down, R, R, C-Left.