Big Urchin

A Mega Urchin is a colossal sub-species of Urchins that first appeared in the game New Super Mario Bros. Wii.

New Super Mario Bros. Wii
In New Super Mario Bros. Wii, Mega Urchins only appear in World 4, and just like regular Urchins, they will float up and down, trying to poke Mario and the others. However, unlike regular Urchins, they are almost invincible, only being defeated with a Star. Even Koopa Shells cannot defeat them, and they could not be frozen. Also, unlike regular Urchins, their pupils follow Mario. They mostly appear along with regular Urchins.

New Super Mario Bros. U
Mega Urchins re-make an appearance in the Wii U game New Super Mario Bros. U. They appear in one of the Sparkling Waters levels, having the same role in New Super Mario Bros. U. In Urchin Shoals, the Urchins and their big relatives are most likely the main features.