Goomby is a little more hot headed than his sister Foomby is, but that does not stop him from using her secret weapon when they get caught: the Goombomb.
Goomby and Foomby make their debut within the adventure book Monster Mix-Up. Here, Mario chases Luigi, but he gets spotted by a Goomba Troopa who warns the duo of his presence as she turns back to the pack. Mario charges the pack and comes back juggling Goomby and Foomby, though the duo use their last-ditch weapon, two Goombombs, to stop him from abusing them. Mario has to find which ones are Goomby and Foomby. If you get the puzzle right, Goomby and his sister will be beaten to death as her Goombombs are discarded before their detonation. However, their Goomba Troopa lackeys manage to kidnap King Toadstool for fusion with Elmo (Monster Mix-Up).
If Goomby and Foomby manage to confuse the player, Foomby will activate her Goombombs.