Sir Frosty

Sir Frosty is an enemy in Spirit Tracks, and is common in the Snow Realm section of the map. These enemies are known for appearing near the tracks occupied by Link as he passes by. They are built like basic snowmen with a ball of snow for a body and a smaller one for a head. As Link approaches, Sir Frosty will launch his head toward Link's Spirit Train to deal damage, eventually regenerating it to continue the assault. They can be easily defeated with the use of the cannon, but require two hits: one for the head and one for the body. Sir Frosty's head can also be destroyed by the cannon in mid-air, preventing it from striking Link.

Trivia
These enemies are similar to Eeno from Majora's Mask.