Infinite Experience Easily
Need to get a level up, but keep dying in the Pit of 100 Trials? Then if you’ve beaten Chapter 5 (The one with the Crags and the Sapiens) go back to 5-4. Remember that pipe that just kept on sending out annoying Sapiens? Just jump on the block right next to it, then use Bowser’s flame, and he just keeps killing the Sapiens, because they just keep coming out, that’s 500 experience every 3 or 4 seconds and 10,000 or 7,500 every minute!

Inifinite 3D with Mario.
Beat Flopside Pit of 100 Trails twice and get Mario’s Card. This will allow you to go in 3D for as long as you want.

Game Arcade
If you go into 3-D mode while in the coffee shop in Flipside B1, you can access a gold pipe that will take you to an arcade where you can play three different arcade games using different functions of the Wii remote, winning prizes for top scores. A fourth game can be unlocked if you have a Gold Card (obtained in the Flopside Milk Bar by going 3-D and opening a treasure chest).

Flea Jump Room Code in Merlees Mansion
In Merlees mansion, when you get to the part where you have to pay off the debt for the broken vase, (and you owe 100,000,000 rubees!) go to the third floor up, and there is a door that is locked with a passcode box next to it. Punch in this code to unlock it: 5963

Now you can get into that room and get a lot of rubees even though you can’t make enough to pay off your debt! (You will ned at least 10,000 rubees to find the 100,000,000 rubees, which are found on the forth floor by flipping to 3-d at the left hand side of the third floor. But you will need an even longer passcode to get through that door at the end.)