House Key (Paper Mario: The Thousand-Year Door)
From the Super Mario Wiki
The House Key is an item appearing in Paper Mario: The Thousand-Year Door. It is an item that Mario must find to complete the "Need a Key!" trouble. Garf lost his House Key, so he can't get back into his house. After Mario returns the key to Garf he rewards Mario with twenty coins. The key is found near Zess T.'s roof in front of the Lovely Howz of Badges.
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