theres actually four secret characters, for the first one you need to open the settings and then click "BIO", then what you need to do is scroll through the characters until you find a game of pong, win three matches by using the arrow keys on your keyboard and you should get the first secret character, for the second secret character you wanna place voice 3, voice 6, voice 8, voice 11, voice 12, voice 14, and lastely voice 15 and once you place all of these characters you should get the second character, for the third secret character you want to click on the settings once again and look at the bottom left corner, you should see some die, click on them, then what you want to do is that you want to throw them into the air until both die have landed on the number 6, after that the die will jumping and then you will unlock the third secret character, for the fourth secret character you want to look at the left of your screen, there should be a little uh cloud there, you want to click on it like five times and just like that you have unlocked all of the four of the secret characters in the game, enjoy! i am glad to help you! :D