For some freaky animals, every day is Halloween.

Take sarcastic fringehead fish, which can look pretty darn scary.

Males of this Pacific Ocean species will fight anything that threatens their eggs or territory, and in doing so open their colorful mouths wide in an intimidating display called gaping.

Battles between these 10-inch fish, a type of blenny, are mouth-to-mouth shoving matches—“nature’s version of sumo wrestling," says George Burgess, an ichthyologist at the Florida Museum of Natural History. (See pictures of nine spooky species.)