HOW TO GET ALL BONUSES... (Don't take this comment down, harry. It's been a week since this mod came out so at least something's going to be spoiled)
Bonus 1 (Cubetron): After progressing Baxter's (Voice 5) bio page, you will see a pong game. Win said pong game 3 times.
Bonus 2 (Enin): Put all 7 human characters together. That's right. 7 polos, 7 characters. These include: Smokehead (Beat 3), Beatsie (Effect 1), Dubstan (Effect 3), Booberry (Melody 1), Xandros (Melody 2), Bubblegoms (Melody 4), and Chippingmin (Melody 5).
Bonus 3 (Dice and Pals): At the bottom of the settings, there are 2 dice. Click and drag on both to roll, get both of them to land on 6.
Bonus 4 (Luna): Click the non-blurry cloud on the left of the screen multiple times. You might need to look hard, since it blends in a bit.