Grand Goombas (also called Giant Goombas, Large Goombas, Mega Goombas, or even (generically) Big Goombas) are a massive type of Goomba found in various games. They commonly behave like regular Goombas except they're larger. Despite their larger size, Grand Goombas aren't any more durable or stronger than a basic Goomba and can be defeated in the same ways.
New Super Mario Bros. Wii
Grand Goombas appear in New Super Mario Bros. Wii where they act as the larger versions of Goombas. They walk slower than a standard Goomba too. Stomping on a Grand Goomba doesn't kill it, instead, it splits into two Hefty Goombas. Grand Goombas are very rare enemies only found in two levels, the World 1 Enemy Course, and World 8-2. Grand Goombas can also be defeated with 3 fireballs.
Super Mario Galaxy 2
Grand Goombas also appear in Super Mario Galaxy 2 where they appear in the Supermassive Galaxy alongside various other giant enemies. To defeat a Grand Goomba, do a spin and then run into it to kick it off the planetoid. A larger version of the Paragoomba called the Grand Paragoomba is also seen here.
New Super Mario Bros. U
Grand Goombas return in New Super Mario Bros. U where they reappear alongside the Hefty Goomba with the same role as New Super Mario Bros. Wii. They are commonly found in Soda Jungle in the level Jungle of the Giants alongside the Gargantua Koopa Troopa and Piranhacus Giganticus.