From the Super Mario Wiki, the Mario encyclopedia
In the Elevator Hall, the concession stand appears to be closed. Luigi is able to look through a hole to see a Goob admiring a gem, then putting it in a safe and locking it. To explore the concession stand, Luigi must enter the men's restroom and have Gooigi pull the chain next to the toilet, opening up the Boo statue in the southeast corner. Luigi then needs to examine the statue. As he does, his hand gets stuck in its mouth and it turns around, revealing the concession stand. If Luigi examines the Boo statue while in the concession stand, his flashlight gets caught in its mouth, and he ends up back in the restroom.
There are tickets and candies scattered on the floor of the concession stand. There are jars of candies Luigi can launch to break open. There are also jars of licorice behind glass Luigi can pull off with a Suction Shot. There are more candies and popcorn on the shelves. There is a cash register and a sink.
There are glass bottles near the north wall with a safe nearby. Luigi can use the Poltergust G-00 to carefully blow or vacuum all of the open bottles in order, from left to right, to spin the peppermint lollipops above and unlock the safe, popping it open to reveal the blue gem.
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