Bristle

The Bristle are spiked monsters made of rock in Paper Mario: The Thousand-Year Door. They have high defense, and if Mario tries to attack one with his hammer, he'll end up hurting himself, since the spikes will pop out once mario gets near. Plus, this monster is impervious to fire.

Technique
The Special Moves, Art Attack, Supernova, and Earth Tremor, will defeat a Bristle, as well as a POW Block or an Earthquake. Mario can even defeat them by just using Superguards.

Notable Bristles
The Poker Faces

Sub-Species
Dark Bristle

Other Games
Although Bristles have made no appearances other then Paper Mario: The Thousand Year Door, they are quickly mentioned in Mario and Luigi: Partners in Time, when, before learning the Bros. Ball move, Young Toadsworth tells his older self that he "looks like he has a Bristle in his britches".