The achievement description can be a little misleading because it seems like this may require some online boosting to get 8 players; however, this achievement can be easily obtained with a single controller.
Select "Start a Party" from the main menu. Set the number of players to 8, and then select 8 rounds as well. I think that the fastest event type is stunt, so choose that for all 8 rounds. Simply play through all rounds as all players and the achievement will unlock as soon as you return to the main menu! It's a little time consuming, but it currently has a very high ratio for as simple as it is to unlock.