Sonic 2: Blue Invincibility:

As Sonic & Tails, use the Super Sonic & Debug codes and go to any level. Then press B to enter Debug mode and spawn a 'TV thing'. Turn into Super Sonic and hit the 'TV thing'. After the blank screen appears, Tails should be invincible with stars flying around him. When Sonic turns back to normal, Tails' invincibility stars will then have a blue tint. Turn back into Super Sonic and the stars will become white again.