Undergrounders (地底人 Chiteijin) are a race of species that appear in all games of the Mr. Driller Series. Although they are not antagonists, they sometimes make a mess of the blocks and food supply. They are considered to be very intelligent, but are scatterbrains. There are 2 races, space and underground undergrounders. In Star Trigon, they are called Uchujin (宇宙人 Uchūjin) and colored yellow, though some sources cite them as "Space Undergrounders".