Wolpertinger

The Wolpertinger is a Bavarian folklore creature as a common trope in jokes between hunters and wanderers. According to the myth it is a hare with deer horns, duck wings, or duck feet and wolf teeth, depending on who you ask.

Hunters would tell their drunk and gullible friends about this creature and lure them into going for a hunt of a Wolpertinger. Of course, it didn't exist, and as such they waited for a long time, until the joke was resolved.