Mega Board Mayhem

Mega Board Mayhem is a board from the Extra Room hosted by Thwomp in Mario Party 4. Thwomp gives no reason as to why he built it, but he claims that it took him six months to make it, and that he is proud of the results. Here, Thwomps are in charge of the shops and many Thwomps, Whomps, and a Ztar hop and dance around below the board.

Unlike normal boards in Party Mode, there are no Stars and Star Spaces found on the board, no special events, and no minigames each turn. Players start with 100 coins, and the goal is to have the greatest number of coins at the end of the game. To do that, there are many Mushroom Spaces and Item Shops around, where the players can get Mega Mushrooms, Super Mega Mushrooms, and other items to steal coins from other players. Players may also utilize Mini Mushrooms and Super Mini Mushrooms to go through the board's two Gates, thereby accessing the inner part of the board, which most notably contains a Lottery Shop.

Item Shops on this board and Mini Board Mad-Dash function differently than on other boards. When visited, they will always have five of the same item for sale, instead of a selection of five different items, and the only items available to be sold are Warp Pipes, Sparky Stickers, Super Mini Mushrooms, and Super Mega Mushrooms. Since all of these items cost at least 10 coins, players can enter the Item Shop if they have at least 5 coins as usual, but they will not be able to buy anything if they have fewer than 10.