Humans

Humans are sentient mammals that don't appear in Happy Tree Friends. In earlier episodes humans seemed to be absolutely nonexistent in the Happy Tree Friends world, however later episodes showed evidence of human existence. For example: In the episode Sea What I Found Russell found a treasure chest that was held by a skeleton that appeared to be from a human. Another example is in the episode Idol Curiosity when Sniffles throws various artifacts down a cursed crack when he was in the museum. Many of these artifacts appear to resemble humans. These examples prove that humans do or at least use to exist in the Happy Tree Friends world. Whether Humans still exist or no longer exist in the Happy Tree Friends world is debatable.