To unlock all levels in UFO Joe, go to the main menu and press the following button sequence:
Up, Down, Left, Right, A, B, Start
If entered correctly, you will hear a sound and the game will reload with all levels unlocked.
2. Infinite Lives:
To gain infinite lives in UFO Joe, go to the main menu and hold the following buttons:
A, B, Start
While holding these buttons, press Start to begin the game. If done correctly, you will have infinite lives.
3. Invincibility:
To become invincible in UFO Joe, go to the main menu and hold the following buttons:
Up, Down, Left, Right, Select
While holding these buttons, press Start to begin the game. If done correctly, you will be invincible.