VS. Mode Player Select
After beating the game, go to vs. mode. Hold down any of the combinations below when you select vs. bosses.
Pixel
L1+R2
Fake Pixel
L1+L2
Pastel
L1+R1
Fake Pastel
L2+R1

VS. Mode (2 player)
Go to vs. mode and while you pick two player tournament, hold any of the combinations below. Player one is listed first, and player two is listed second.
Pastel vs. Fake Pastel
L1+R1
Fake Pixel vs. Fake Pastel
L2+R2
Fake Pixel vs. Pixel
L1+L2
Pastel vs. Fake Pixel
R1+R2
Pixel vs. Fake Pixel
L1+R2
Fake Pastel vs. Pixel
L2+R1
Fake Pastel vs. Pastel
L1+L2+R1