Big Boo's Riches:
In Big Boo's room, turn to the right as soon as you enter. Use the vacuum on the two torch fountains there to get a gold bar from one and some cash from the other.
We Love Options:
Rescue Mario and beat the game once. You will get a rank based to how you did and receive a letter grade. Save your game. You will now have the option to restart Luigi's two different ways (in addition to going to the completed Gallery). The first option lets you go back to the regular Luigi's Mansion Mode. The second option, called Ura-Yashiki (Another Mansion) in Japanese, lets you restart the game -- and presumably some of the things in the mansion have been changed around.
Mice Mean Riches:
If you want to recieve an 'A' grade you need to locate all the golden mice. To locate the mice, go into 1st person mode with the gameboy horror and click onto hidden cheeses with the A button. These cheeses can be found in:
The 2nd floor study behind a desk.
The 1st floor dining room underneath a chair.
The 2nd floor dining room at the back.
The 1st floor room with the crystal ball behind the fortune teller.
The 3rd floor trophy room behind a chair.
The 2nd floor corridor near the stairs to the attic, you hear a chime and a mouse runs up the corridor. (You don't need to find cheese for this one).
As soon as you click on cheese a mouse appears, go back to 3rd person view and suck up the mouse quick for much cash and the occasional gem.
Secret Treasure Rooms:
The mice can only be caught before the lights turn on in any room. Grab the mouse and then get the ghosts. If you miss the cheeses the first time around; go mouse hunting after the third boss when the lightning trips the power and the mansion is in darkness again. Although in some rooms, now there are loads of ghosts, so it's not as easy as it was the first time round.
The first one is located on the 1st floor, in the south-west corner of the Mansion. After you have sucked in the candle-carrying butler, check out the room with your Game Boy Horror to locate a mousehole. Press A to activate it and go inside to enter the trasure room. The 2nd treasure room is accessible from the roof top. Use the elevator in the toy chamber to get on the roof, then go all the way to the right and climb up on the chimney. Fall down and you will land in another treasure room.
Water the Plant:
Go to the right side of the graveyard. It's Just underneath the balcony with toad. There is a seed. Once you can use water, (BEFORE the 2nd boss) water the seed. Enter the doghouse, and defeat the 2nd boss. Return to seeding and water again. continue with the game, but come back and water the seed after you fight the 3rd boss. It will bloom and produce a diamond!
If you're running low on lifeforce, get out your vaccuum and start cleaning lamps and vases. Almost every second vase has a heart hidden inside -- and nearly every lamp or chandelier either yields money or health. Happy hunting.
Reward for 50 Boos:
One of the sidequests in Luigi's Mansion is the capture of the 50 Boos that you released accidentally in the beginning of the game. Finding Boos can be a time-consuming task as you have to make your way through the whole mansion and track them with your Game Boy Horror "Boo Sensor." Boos like to hide in rooms with the lights on, so be sure to check in every nook and cranny. A blue light on your GBH means there's no Boo to be found, a yellow light means you're close, and red means you're right in front of the hiding ghost. If the light is red, switch on your vaccuum or examine the object in question with A. Watch out, though, not every red light equals a boo. Sometimes a Boo Ball will fall out (you can simply blast it at a wall or leave it where it is), or a bomb that has the potential to cause some damage -- so run! If you're having problems finding all 50 Boos, be sure to look in the "door-less" treasure rooms.
The reward for catching all 50 Boos is a large diamond.
Secret Warp Zones:
Running around from one end of the mansion to the other can be a very time consuming task. Thankfully, Nintendo has implemented hidden warps that let you zoom back to the entrance hall. Basically, any mirror in the mansion (except for the large one that reflects the invisible ghosts) can act as a warp. To warp using a mirror, switch to your Game Boy Horror's first person mode and examine the mirror with A. After a really trippy warp sequence, you will find yourself in the entrance hall of Luigi's Mansion.
Golden Mouse Location:
First floor corridor (by the fortune tellers room) listen for the chime and the mouse will appear and run down the hall.
Making the Grade:
To recive the A grade you need to collect at least $100,000,000. Tip, just before you beat the final boss strip search the mannor to find any more money, and DON'T FORGET to water the plants.
Beat the Second Boss:
With your Powergust 3000, suck up the black ghosts and then it will turn into a ball. Then shoot the ball at the pink ghost that shows up once in a while and the pink ghost is now covered in the ball. Then shine your flashlight at the pink ghost and then start sucking him up. You will have to do this several times because is is a very hard boss to beat!
Getting a Bigger Mansion:
Once you've beaten the game you will get a grade. Once you have gotten your grade it will show you a picture of your mansion if you get a "c" you will just have a regular house, if you get a "b" you will have a mansion, but if you get an "a" you'll have a gigantic mansion.
Quick Health Fill:
To fill you health fast if you are low. Look at any mirror with the GBH and click on the A button (I think). This will warp you back to the entry of the mansion. Then go upstairs and to the left to the Nursery. In the dresser in the upper right of the room there is a large heart (worth 50) and you can get it over and over again. I think you can even leave the room and come right back in and get it again. You can do something similar in the basement in the room across from the room with the circuit breaker. In the room with the dust piles on the floor, vacuum the middle of the shelving unit in the middle of the room. This will give you a large heart. You can leave the room and come back in over and over to fill your health.
Thanks to Revolution readers Jaames, Code Cing, Michael "Mario" Fowlkes, Sam, Tyson Smith, Mike, Carlos Chavez, Matthew J. Remick and Diddy Kong!