Rextro and his arcade game are off on the far right side of the map on the first Grand Tome World, Tribalstack Tropics. In order to use his arcade game, you need to find the coin on the level. The coin is located beneath where he is located, in a cave along the cloud racing track. After finding the coin, go speak with Rextro to play his racing game. Completing the 5 laps in under 5 minutes will net you this trophy.