Just beat Flopsides Pit of 100 trials.
To do this, you must get the Golden Card.
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.
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.
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).
(Tiptron is just like Tippi) Buy it from Francis after you beat the game for 999 coins!!!
(Piccolo makes melodies that trigger in-game events and cures some status problems) Place the 6th pure heart, talk to Merlee and help her, talk to Merluvlee, then Bestovious, Watchitt, Merlumina, then Merluvlee to get Random House key
(Dashell makes you go really fast) The bottom of Flipside Pit of 100 trials
(Barry provides a force field that protects you and can hurt enemies) Beat Francis in chapter 3-4, then find Barry behind a bush in chapter 3-1.
Acquire a Golden Card found in a treasure chest in the back room of The Overthere in Flopside.