Floor 3: Hotel Shops

Exit the elevator and use the Dark-Light on a fake lamp on the face wallpaper behind green plants to the right to find bars. Send Gooigi through the bars to access a chest of Gold. Find Bills in the plants on the other side of the elevator. A map to the west is in front of the plants.

Head east toward the bathrooms. Find Coins in a trashcan and a phone on the counter. Use Dark-Light on the floor to reveal a second phone. Use it to summon a Golden Goob. Defeat it with Strobulb flashes and slams for Gold.

Enter the men's bathroom. Use Suction Shots to open locked stalls. Flushing the left toilet reveals a fake ghost and yields Bills. The right toilet contains a Key.

Look in the mirror above the sink. Use Dark-Light on the floor tiles to reveal a hole. Let Gooigi pass through. Head right to kill Spiders for Bills, then west under the women's bathroom, killing more Spiders. Take Gold Bars at the end of the passageway. Return to the valve and blow on it to turn it, restoring water to the women's bathroom.

Take control of Luigi. Use a Suction Shot on the lid on the wall to the left. This reveals a pipe for Gooigi to reach the women's bathroom and obtain the floor's Purple Gem. Open the toilet for Coins, inspect the trashcan for Gold Bars, and turn on the sink for more Coins. Exit the restroom with Luigi.

Head left to the locked revolving door and use the Key to access the shops.

In the Mall Lobby, you will spot the boss, Kruller. He flies into a room, leaving behind a diamond-shaped key.

Go up the escalators and turn right. Inspect the trashcan for Coins. Tear off the fake poster on the eastern wall to reveal a Coin painting, which can be revealed with Dark Light.

Head east into the hallway and grab the Diamond Key. Peek into the open window to spy on Kruller.

Use your Strobulb on the Strobe Switch on the vending machine for a Coin, then a Bill, then a Gold Bar. Flash again for a Rat and its Coins, then five Rats and their Coins. The final flash yields the floor's Blue Gem. You can optionally use a Suction Shot to bring down the vending machine for tomatoes. Return to the lobby.

Head northwest in the mall lobby. The shop with the Diamond inscription is in the northwestern corner. The entrance is blocked by bars. Send Gooigi through the bars.

In the accessories store, have Gooigi insert the Diamond Key into the cash register in the top-left corner to reveal the Heart Key. A Goob will appear and attempt to take the key, initiating a fight.