Jump on him every time he is underneath you. You will master it on youre second time around. He will give you 300 experience every time you jumpo on him and it will let you hit him for about 15 or more times. Making each experience for each koopa 4.5k or more each. And be sure to grabthem. Not the shells they kick at you.
These give you 30HP and if you go back into the pipe and come back he’ll reappear. You can get about seven or eight Whacka Bumps before he disappears for good. That’s at least 210 HP for free.
Use your Return Pipe then go back into the red door to get to 1-2. Continue through the area until you get to the town. The third house is Watchitt’s. He will send you on your fourth fetch mission to see Merlumina.
Use the Return Pipe and go back to the red door. Choose to go to 1-4 and travel through the whole chapter. At the end (past where you fought Fracktail), you’ll go into a house and when you run towards the star Merlumina will appear. After a lengthy bit of text, she’ll sign the autograph and you can return to Watchitt in 1-2.
Then go back to 1-1 to give the “you-know-what” to Bestuvius, and then to Flipside to give the Training Machine, a Nintendo DS, to Merluvlee. Finally take the Crystal Ball from her to Merlee in Flopside and she’ll give you a key.
This key can be used on the locked door in Flopside. The door is on the 1st floor through the piece of the wall that you bombed earlier. Inside you’ll find Piccolo. There are only two place I have found to use him.
Go to the 2nd floor of Flipside, flip to 3D and go through the gate across from the White Tower. Instead of crossing the bridge, return to 2D and go to the left of the screen. You’ll see a pipe up above. Use Boomer to blast the bricks and enter it. You’ll now be on the 3rd floor of Flipside.
Piccolo can be used on the block with the music note, which is all the way to the right. You’ll get a Merlee card. In the same place in Flopside you’ll get a Nolrem card.
These are the only place I’ve found so far to use Piccolo.
After doing this you will be sent into a huge ball where you run to make volts. You are paid if you stop and tell him that you are tired. But, instead of running yourself just get a heavy object (not too heavy) and have Mario (or Peach) go to the right of the circle. Put this heavy object on the left button (up if contoller isn’t sideways) and go do something else.
Come back later and stop, you have just gained many rubees without wasting valuable time.
That opportunity never comes up again but the coins you get are well over the maximum 999 Mario can carry. Two “bone breaking” installments should let you exploit this hapless run-down to the max.
With 100 coins, go to Flopside’s first floor through the blasted wall and enter the card shop called Fondest Hopes. Talk to the sales clerk at the counter and select “Buy a Catch Card SP” then say “yes” he’ll give you the card, then say “no” when he asks if you want more Catch Card SPs.
After you have a Catch Card SP, leave the shop use the return Pipe Merlon gave you in the beginning of the game which will return you to the top of Flipside Tower.
Go to the Light Blue door and select chapter 5-2. Go through the door at the end of the first stage (not chapter, but rather the area you first arrive in). Turn right and go past the pipe above your head past the next 3 pipes.
Next, enter the door next to the two blocks that is also next to a Cherbil. Clear the gap and you will come to a Stone Buzzy. Kill the Stone Buzzy, and where you land after you kill him flip the world to 3D.
Immediately you see a yellow flower enemy called an Amazy Dayzee. Quickly go to your quick menu by pressing 1 and 2 at the same time, use the Catch Card SP and turn the enemy into a card.
If the Amazy Dayzee flips to 2d do not use the catch card while in 3d, flip back to 2d and then use it.
Grab the card then use the return pipe again. Go back to the shop where you bought the Catch Card SP sell the Amazy Dayzee card it is worth a whopping 300 coins then you can buy 3 Catch Card SPs. Repeat ad nauseum.