From the Super Mario Wiki, the Mario encyclopedia
The Thorny Bathroom is a bathroom covered in some thorny vines and brown leaves. There is a toilet, a bathtub, and a sink. There are also piles of brown leaves on the floor. Underneath them are coins and Gold Bars. In the southwest corner, on the bench, is a vine that Luigi can pull using the Poltergust G-00, and doing so will destroy the vine. The same thing can be done at the sink. There is a trash bin that Luigi can grab using the Suction Shot and then fling to destroy certain objects. This way he can destroy the sink, bench, toilet, and the front of the bathtub. Upon destroying the toilet, Luigi will be able to pull on the vine and then destroy it which unblocks the path outside of the room, in the Atrium. When Luigi tries to leave the room, a Slinker and a Hammer will appear. Upon defeating them, Luigi will be able to continue.
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