The Flipside Pit of 100 Trials is a dungeon found in Super Paper Mario. It is a labyrinth of 100 rooms. Each room has a different set of enemies, one of which has a key to the next room. If Mario completes ten floors, he can go in a black pipe to exit the pit, or he can go to the Big Black Treasure Chest to get a Collectible Card. The collectible cards from this pit are sidekicks from the original Paper Mario.
At the end of this pit, Mario must face the stronger counterpart of Fracktail, the boss of the first world. It is known as Wracktail, and has higher attack power as well as HP than Fracktail, making for a tougher battle.