Snipe hunt

A snipe hunt is one of a class of practical jokes that involve experienced people making fun of newcomers by giving them an impossible or imaginary task.

Inexperienced campers or hunters are told about a bird or animal called the snipe, as well as a (usually ridiculous) method of catching it - such as running around the woods carrying a bag, or making strange noises. Since the supposed snipe doesn't exist, the hunt never succeeds, no matter how foolishly the newcomer acts.

(There is a species of bird called a snipe.)

Another variation of this type of practical joke, called a fool's errand in the UK, involves sending newcomers on a work site to fetch nonexistent tools, such as a left-handed screwdriver.