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The Birdcage is an item in Paper Mario: Color Splash. Mario can find it in room 303 in Dark Bloo Inn, where a Ghost Toad says that his "red bird" escaped from it. Mario must recolor the Birdcage to collect it. When Mario talks to a Toad that is trying to catch a red bird outside, Huey will suggest that he should try to use the Birdcage. The "red bird", which is actually a Koopa Paratroopa, will then fly into the cage.
After Mario picks up the cage again, it will be called the Caged "Bird". Mario must take the cage back to the Ghost Toad in room 303. The Ghost Toad will put the cage on the table, and then he will leave to go to the tea party. If Mario speaks to the Koopa Paratroopa in the cage, he will complain about being called a bird.