The Mario Party World is an alternate dimension and main setting of the game Mario Party 3.
Mario, along with his friends, are enjoying their day until a large star crashes down. Mario then picks up a Mario Party board game and the rest are happy to see who the Superstar is. However, the star suddenly starts glowing and Mario and the rest find themselves inside of the board game itself. The dice, Tumble, then warps Mario and the rest away and the Millennium Star introduces himself to the player before crashing down onto the map.