Captain Goomba Trial
From the Super Mario Wiki
This is the second of seven bonus levels that involves the captain battling enemies by themselves. Captain Goomba is the selected captain to enter this level.
There are three battles in this level; the first has some Beanies in the front lines, as well as a Gritty Goomba captain. The next one has two Rexes, as well as a Limbo Bro captain. The last one has several Paratroopeas, as well as a Clumph captain which is when the player must use Captain Goomba's signature command, Clash of Captains.