This is probably a easy way of getting most bonus parts the first time round.

Whenevr you roll down a hill/jump off somewhere you may see a curved wall flicker it's transparency, (Seeing through it) All you have to do is jump into it and there will be a bonus area with missing bonuses.

Always explore and you will have most parts the first time round and you will only need a few more after the end.

To access this, just simply create a projector in the MuiMui house, but finding the parts could be pretty hard.