From the Super Mario Wiki
Dream Snowball Fight is an event in Mario & Sonic at the Olympic Winter Games. It only appears in the Wii version of the game, but a similar event appears in the Nintendo DS version.
Dream Snowball Fight has teams, with four players to a team. The goal of the game is to chuck snowballs at the opponents, while trying to avoid being hit. There are also items, which makes the game similar to Mario Kart. The music is based off of the music in the winter levels of Super Mario 64.
- Dream Snowball Fight, along with Dream Gliding, are the only Dream Events in Mario & Sonic at the Olympic Winter Games that do not take place in the Mario or Sonic Universe. Instead it takes place at Christmas Village.