The Trio's Last Stand
From the Super Mario Wiki
Private Goomp, Sergeant Guy, and Corporal Paraplonk finish planting the time bomb on the Koopa Cruiser that Roy mentioned earlier, only to be stopped by Captain Goomba, Captain Shy Guy, Captain Boo, and Captain Koopa Troopa. The two sides face off, along with Koopa Troopas, Koopa Paratroopas, Fly Guys, Bandits, Shy Guys, Goomba Towers, Big Tail Goombas, and Paragoombas. When the bomb is finally defused, the other captains, standing on the deck of the Koopa Cruiser along with Lakitu, praise Captain Goomba for his leadership, while he, along with Private Goomp, patiently stand in the cargo area and experience nostalgia in the place where the journey began, with a small cutscene at this point showing that it was indeed these two Goombas who were the first ones that the Mario Bros. fought in the beginning of the whole adventure.
1 - Despite not being shown in any of the level's battles, this ally can be recruited whatsoever.