Paper Mario RPG

In X-Naut Fortress, go in to the ventilation shaft in sublevel 2 and drop through the far right vent in to the dressing room. Open the curtain of the stall you fall in to and Mario and all his partners will become 8-bit (they will look as they would on an 8-bit system like the NES) until you leave the room. Entering the room the normal way via the door and going in to this stall, closing the curtain, and opening it again will not work.

After you sign into the Glitz Pit and win a few fights, come into the main lobby to see Rawk Hawk being adored by his fans. Use Mario's Hammer or Flurrie to get rid of the fans, and when all of them are gone, Rawk Hawk will get mad and scold you.

In Creepy Steeple, after you've freed the Boos, stand still in the main room.
Wait for some Boos to start sticking to you, the use your Super Hammer attack to shake them off. Do this twice, and the Boos will get mad and form the Atomic Boo. When beaten, he will drop the Lucky Start badge. This is needed if you want to fill up your Tattle Log and get all badges.

On the shelf in the top-right hand of the screen in Professor Frankly's house, you'll find the solution for the 4 statues in Boggly Woods.

As soon as Chapter 1 is available you can buy as many Sleepy Sheep as you can carry and/or store at the Rougeport Toad Bros. shop and you can sell them all at the Petalburg shop for a 2 coin profit each. Doing so will also give you 1 store point per Sleepy Sheep and an item per 10 store points, most of which are normally difficult to get at this point in the game. This strategy can be used to help defeat the Pit of 100 Trials before defeating Chapter 1's boss, among other benefits to having late game items early.

Need more Turtley leaves for all of Zess. T's recipes? Easy. One way is to solve Kroop's trouble and he'll give you a Turtley leaf. If you ever need more, simply go in front of his house and behind the front fence and there'll be 3 bushs. Rattle each one and one of them should give out one. The bush that gives out the leaves always change and when you get one, you have to go off screen first and then come back. Quite handy if you want all the recipes.

In the Palace of Shadow, during the cutscenes before you fight the Shadow Queen, she will ask you if you want to join her (make sure you saved before the cutscenes). If you choose 'Yes', you will get a weird ending for the game in which you join the Queen, and get a 'Game Over'.

Complete the ??? problem at the Trouble center by finding the secret badge hidden in Hooktails castle. Return the badge to the mosue ontop of Zess T's shop, and she will join your team.

This really won't help you in your game, in fact, save before you do this, or you'll lose some game data. -- When you find the Ragged Diary in the Excess Train's Baggage Cart after meeting the ghost, read the diary and the ghost will appear out of nowhere really angry and curse Mario, earning you an instant game over.