In the Super Mario Bros. film, Goombas are former residents of Dinohatten, a city inhabited by dinosaurs that survived their extinction event 65 million years ago and have since resided in a parallel dimension where they have continued to evolve into a human-like state. Goombas were once normal Dinohattenites but broke the laws of President Koopa and were punished by being forcefully de-evolved into a more primitive state. They appear as huge humanoid reptiles that wear long red coats with spiked shoulder pads and serve as the backbone of Koopa's army. They are lethal and loyal, but also completely stupid. The Mario brothers easily manage to evade them and distract them during their adventure in Dinohatten, even convincing a group of them to start dancing to elevator music when they sneak into Koopa Tower.
Goombas may not be smart, but they can be dangerous. They are physically strong and they are armed with fireball-launchers and Devo-guns that can de-evolve other creatures. Koopa had planned for his Goomba army to invade the human world and use these weapons to de-evolve the human race into apes.