Travel to MJ's Face-R-Us and enter the following case sensitive (without the quotes) coupon codes to unlock the corresponding character.

Unlock Anthony Carboni:
Enter 'CARBONI'

Unlock Destructoid Staff:
Enter 'DTOID'

Unlock Electric Playground Television Hosts:
Enter 'ELECPLAY'

Unlock Epic Meal Time:
Enter 'EMT'

Unlock Maxime's Friends (RCR Game Artist):
Enter 'MAXIMEAMIS'

Unlock PJ Fresh Phil from YTV:
Enter 'PJFP'

Unlock Polytron:
Enter 'POLYTRON'

Unlock Gaijin (Bit.Trip) Staff:
Enter 'GAIJIN'

Unlock Mojang (Minecraft) Staff:
Enter 'MOJANG'

Unlock Team Meat (Super Meat Boy) Staff:
Enter 'TEAMMEAT'