Cavemen are tricky. You need to balance the scraggly beard with the animal skin clothing. You need to get the extra body hair right, and they need to be just slightly thicker and shorter than the other characters.
That being said, the absolute worst part is naming them.
It needs to be short — one syllable if possible, and preferably not more than three letters. Here’s some choices I discarded before landing on Og:
See, it’s harder than you’d think!