Which Mario Party game introduced the Mega Mushroom item?

Mario Party 4 introduced the Mega Mushroom item. The 2002 GameCube game made it a central part of its item system, alongside the contrasting Mini Mushroom.

Using a Mega Mushroom enlarged a character and allowed them to roll two Dice Blocks, potentially covering a much greater distance than a normal roll. A giant player could also crush opponents encountered along the route and steal 10 coins from them. The effect was powerful, but it also changed how the player interacted with the board and could prevent some normal board actions.

The Mini Mushroom worked in the opposite direction: it shrank the character, restricted the Dice Block to numbers one through five, and enabled access to small pipes and shortcuts on certain boards. Mario Party 4 also included a Super Mega Mushroom variant, which let a player roll three Dice Blocks.

The Mega Mushroom is sometimes associated primarily with New Super Mario Bros., where it later became a giant power-up. However, Mario Party 4 was its first appearance in the Mario franchise, preceding the 2006 Nintendo DS platformer.