Bowser's Gnarly Party is the final board in Mario Party 4, unlocked by beating the board in Story mode. It is a board located in the sea of lava and is hosted by Koopa Kid. He built it in honor of Bowser's greatness and wanted the players to have fun on it – whether they wanted to or not. It has a difficulty rating of 3 out of 3.
The main gimmicks of this board are Bowser and the two sets of stone bridges. The stone bridges break down after 3 player passes it and another stone bridge rises up in the other direction.
The Happening Spaces will cause the Bowser head statue in front of the spaces to breathe fire, destroying one of the player's items. They are all behind gates.
The Item Minigame is located in the lower left and is called Koopa Kid Shuffle. The Koopa Kid shuffles 3 items around and the player chooses one. That box is locked and he does it again with the two remaining boxes. After two boxes have been eliminated, he gives the player the remaining one. The coin minigame is located at the top of the board and is called Brake Bullet Bill. The Koopa Kid fires a Bullet Bill and the player has to mash A to stop it. The better it is stopped, the more coins earned.