In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Example input: Passage: Nearing London, Oliver encounters Jack Dawkins, a pickpocket more commonly known by the nickname the "Artful Dodger", and his sidekick, a boy of a humorous nature named Charley Bates, but Oliver's innocent and trusting nature fails to see any dishonesty in their actions. The Dodger provides Oliver with a free meal and tells him of a gentleman in London who will "give him lodgings for nothing, and never ask for change". Grateful for the unexpected assistance, Oliver follows the Dodger to the "old gentleman's" residence. In this way Oliver unwittingly falls in with an infamous Jewish criminal known as Fagin, the gentleman of whom the Artful Dodger spoke. Ensnared, Oliver lives with Fagin and his gang of juvenile pickpockets in their lair at Saffron Hill for some time, unaware of their criminal occupations. He believes they make wallets and handkerchiefs.
Example output: Who believes Fagin's gang make wallets and handkerchiefs?.
Example explanation: This question is based on the following sentence in the passage "He believes they make wallets and handkerchiefs". It evaluates the understanding that the pronoun "he" refers to name "Oliver". You can ask questions like this one about most pronouns in a paragraph.
Q: Passage: The story begins with a farm mother scolding Jack for trading his cow for five seemingly worthless beans. The beans are thrown out a window and land under Sylvester's cat bed while the lazy cat is taking a "catnap". Instantly, the beans sprout into a giant beanstalk that reaches into the heavens, taking the still sleeping Sylvester with it. The puddy tat awakens and is startled at how everything seemingly grew overnight. Eventually, he walks inside a castle and instantly spots a giant birdcage (with a giant Tweety singing inside). Sylvester opens the cage and chases what he says are "acres and acres of Tweety Bird." However, Tweety's master comes into the room; after Sylvester hides, the master puts Tweety back in his cage and hangs it on a high ceiling; that way, he will not get into any mischief while he is gone.
Sylvester makes several attempts to get at Tweety, having to overcome both the cage being on the ceiling and dodging a giant bulldog who is trying to chase the cat away. Each of Sylvester's attempts to get the bird ends unsuccessfully; several times, he is barely able to get away from the bulldog. At one point, he encounters a real giant mouse, only to have both of them get scared of each other and run away in opposite directions.
A:
What is the name of the character who enters a castle and finds a giant birdcage?