As Wario, go outside to the Boo-infested courtyard. Position yourself so that a Boo is between you and the rabbit. Run and dive for the rabbit. As you do, the Boo will solidify and knock you away while you catch the rabbit. Then walk back to the rabbit. It will not move, but it is now untouchable, like a Boo when it transparent. This can also get funny screenshots if Wario stands inside the rabbit, which makes it look like Wario has rabbit ears.