Choombas are large mechanical locomotive-like subspecies of Goombas who appear in Mario & Luigi: Bowser's Inside Story & Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey. They are located in the Underground Tunnel.
These enemies usually battle with Coalbits who make Choombas faster when they jump in them. Choombas attack by puffing smoke out of their heads to show how they are going to attack Bowser. The spiky shell means Bowser has to duck as the Choomba is to jump directly over him and the fist means Bowser has to punch Choomba before it rams into him.
They also appear in the Fawful Express fight and groups of four of these enemies come out of the locomotive to attack Bowser. Bowser can defeat these enemies by stomping on them in the area in which they are charging in. These have been known to power trains
- Choombas were going to be fought by Mario and Luigi, but the idea has been scrapped out for unknown reasons. They puff out smoke in this battle with them. The M means it is going to attack Mario and the L means it shall do it to Luigi. They can be countered by hammers when they were to attack the bros.