Herpfish

"You know the odd slug things in the Crimson that jump around and look very creepy?  Legend tells of a species of those that's part fish!  I want you to go catch me one so I can put it in [Dryad's Name]'s bed!"

~Angler Quest Log

The Herpfish is a quest fish that can be obtained by fishing in the Surface Crimson. The angler will only assign this quest if the dryad is present.

Trivia
This - along with herplings, derplings, and derpfish - is a reference to the Herp Derp meme.