In the final stages, you need Logo Parts to open the back door in the Vault.
To activate the projector in the Puppet Shop, you need the Mechanical Wing , the Parrot Head , and the Doll Part .
In Chapter 6 (First Tower), you must retrieve a Clay Tablet to solve a color-matching puzzle on the door.
In Chapter 1 (Girl's Bedroom), you must find a mechanical doll part on a headless doll on the bed.