The Mountain Goat
From Homestar Runner Wiki
The Mountain goat is first seen in In Search of the Yello Dello. It is assumed that it is Marzipan's goat because it later appears in the game Audition with Marzipan. Further evidence appears in the Yearbook Character Page, when it mentions Marzipan tending to her herd of goats. Only its head and neck are ever seen.