Spiko is a small, deep green reptile that is covered in thick fur, which looks like pine needles. A significant feature of this creature is its large lower jawbone, which it never opens. It has pink feet with three toes and bright red eyes, and two horns on its head each sprouting out left and right. Its quills are green with yellow tips. Its tail is about half the length of its body with a round end with bumps and spikes covering it, having a distinct yellow double 'S' pattern.
As its tail is dextrous, it often displays its emotions though tail movements in animations for all 3 games. When happy, Spiko raises its entire body, supporting itself off the ground by the mace-like tail end. When idle, it rolls the appendage from side to side. The muffled voice it had in Origins may be due to the fact that it has never been seen opening its mouth.