Monty Bros.
The Monty Bros. are a group of four Monty Moles seen in Mario & Luigi: Bowser's Inside Story. They are minions of Bowser, first encountered in the Underground Tunnel beneath Cavi Cape. Here they are seen using a large drilling machine to drill a tunnel through to reach Toad Town, claiming to be making an escape tunnel for Bowser to use after he has kidnapped Princess Peach, straight back to Bowser's Castle. They had already drilled from Bowser's Castle to Cavi Cape, almost reaching Toad Town. Bowser, who had just spotted them, said that he did not remember giving that order, but helped them nonetheless. The player would then go through a mini-game where Mario and Luigi, inside Bowser's body, would stimulate his leg muscles to push the giant drill before its battery ran out (or in this case, ninety seconds of mini-game time).
Later they are seen in the treasure vault of Bowser's Castle, seeing Bowser again, but they had built railway tracks around their tunnel. After seeing Bowser's shocked face at the tracks, the Monty Bros. reveal that they had switched sides, over to Fawful. They then jumped into the Fawful Express, the reason they had built the tracks. The huge cargo train would then proceed to push Bowser all along the train track, slamming him into a colossal boulder. Bowser would then be re-awakened by Mario and Luigi, turning him giant. A battle with the Fawful Express and the Monty Bros. would then start. After Bowser had destroyed the train, the flying bits of debris from it slammed into the Monty Bros., ultimately defeating them. It is unknown if they survived, as they are not seen for the rest of the game, nor did they fess up and rejoin Bowser's military at the end of the game.
