All levels (PAL)
At the "Era Selector" screen, hold L2 + R1 and press X, Square, R2, L1, Circle, X, Square, Square, Square.
Stack It
You can stack up multiple items by carrying one, jumping onto the other, and then dropping the first one. Then you can carry both at the same time. If you want to unstack them, just throw them with the Kick button.