Giant Shelly

A Giant Shelly is a snail enemy found Underground. They attack by curling into their shells and hurling themselves at players, though they will stall in midair and drop to the ground if they are damaged during their flight. Giant Shellies attack very quickly and deal high damage for the stage in the game where they are found.

Giant Shellies are unique in that their ability to spawn is connected to two other Cavern enemies, the Crawdad and Salamander. Of these three enemies, a world will choose two types that it can spawn, leaving the third inaccessible. Giant Shellies will never spawn in a world that features both Crawdads and Salamanders together.

Trivia

 * Like their aforementioned analogs, Crawdads and Salamanders, Giant Shellys have multiple colored variants. Also like said analogs, these differently colored variants are statistically identical, unlike various Zombie varieties.