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 top. Their name comes from "wall", referring to them being moving walls, and possibly a pun on the term "wall-eyed", a condition that causes a person's eyes to drift apart from each other.

Super Mario 3D World / Super Mario 3D World + Bowser's Fury
Walleyes first appear in Super Mario 3D World as rare enemies. They move from side to side in an attempt to keep the player from walking past them. Contact with the spikes on their sides and top causes 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 Lucky Cat Mario or White Tanooki Mario. They only appear in Ty-Foo Flurries, The Great Goal Pole, and Mystery House Marathon.

Captain Toad: Treasure Tracker
Walleyes return as somewhat uncommon enemies in Captain Toad: Treasure Tracker and its Nintendo Switch and Nintendo 3DS ports, serving the same purpose as in Super Mario 3D World. The only way to defeat them is by using an Invincibility Mushroom, and they provide the player 3 coins upon defeat.

Minecraft
In the premade world for the Super Mario Mash-up in Minecraft, small 3D pixel art resembling a Walleye appears in the snow area.

Super Mario Party
Walleyes appear in Super Mario Party as non-playable characters. They can appear in Follow the Money as obstacles, where they run back and forth constantly, and they can also be seen in Absent Minded.

Names in other languages
Guckiwummps Wallokkio