Snailicorn

Snailicorns are large snail-like creatures that sport a single horn on their heads, as indicated by the species name (a portmanteau of snail and unicorn), as well as feet.

They appear only in New Super Mario Bros. and are never seen outside of ice stages. Snailicorns are resistant enemies, as jumps are not enough to defeat them, and fireballs are ineffective. However, as jumping on them pushes them back, this tactic can be used to send them off of cliffs, though they will reappear if Mario leaves the area and comes back. Also, a full-speed Shell Mario or a stray shell will knock them out.

Snailicorns always charge in a straight line, but change direction at edges. They only appear in World 5-3 and World 5-B.

Trivia

 * The game's internal filename for Snailicorn is a romanization of the Japanese name for Bully, suggesting that it was originally designed as one before being changed to a horned snail. This explains why they act in almost the exact same manner.