When Willie has escaped from you and runs to Astro Land, use the camera cheat. Then go and look for Willie near the giant statue of Von Clutch. You should see him floating inside of a wall. Technically, Wille was never removed, just put somewhere else.
Unlock Evil Crash Costume On Mystery Island where you find Cortex there's an owl shaped lamp behind him. If you hit the body-slam switch it will rise up. When you enter the cave go right and speak to the drone at the top of the island and pay 2000 coins to get the Evil Crash Costume.