Walleye

Walleyes are Whomp-like enemies that first appear in the game Super Mario 3D World. They are similar to the Wallops in Super Mario 3D Land, with spikes on their sides and back.

Super Mario 3D World
Their first appearance was in the level Ty-Foo Flurries. They move from side to side in an attempt to stop the player from walking past them. Contact with their spikes will cause damage, but their fronts and backs are safe to touch. Walleyes can be temporarily dazed by a projectile or a claw attack and can be destroyed by Golden Statue Mario.

Captain Toad: Treasure Tracker
Walleyes return in Captain Toad: Treasure Tracker, with the same purpose as in Super Mario 3D World.