Humans are sentient mammals that don't appear in Happy Tree Friends (anthropomorphic animals take their role). In early episodes, humans seemed to be absolutely nonexistent in the Happy Tree Friends world. However, later episodes showed evidence of human existence.
Whether humans ever existed or not in the Happy Tree Friends world is debatable. Perhaps the skeleton and the other evidence was meant to portray other "anthropomorphic" primates, like Buddhist Monkey and Sensei Orangutan. It is unknown if humans will truly appear in in the show (though unlikely). If they do, it is unknown what they would look like in Happy Tree Friends style.Despite the evidence, Kenn Navarro confirmed that humans do not exist in the world of Happy Tree Friends.
These instances imply evidence that humans do (or at least did) exist in the Happy Tree Friends world.
- Perhaps the most glaring example, The Cursed Idol itself looks humanoid in appearance, possibly made from Mesoamericans. Some other objects in the series (i.e., lawn gnomes in Snow Place to Go, a doll in Clause For Concern) may also bear humanoid features. Had these objects been made by animals, they would have resembled the Happy Tree Friends style.
- In Sea What I Found, Russell found a treasure chest that was held by a humanoid skeleton. This same skeleton was also seen underground in A Hole Lotta Love.
- In Idol Curiosity, Sniffles exhibits several objects in the museum. Many of these artifacts, like the suit of armor and Moai head, appear to resemble humans.
- In A Sight for Sore Eyes, there was a poster of what looks like a human eye.
- In Easy For You to Sleigh, A suit of armor fit to a human body shape was seen in Flippy's house.
- In Ski Patrol, Intimate Spotlight, YouTube 101: Subscriptions, and YouTube Copyright School, clear English voices from unseen characters are heard narrating the story, sometimes interacting with the other characters. It is possible that they could be humans. This may also apply with The Interviewer in Intimate Spotlight.
- A stoplight in And the Kitchen Sink appears to show both human and HTF traits. A happy tree friend silhouette is seen for the "Walk" sign, but a human's 5-fingered hand (rather than a tree friend's 4-fingered or mitten-like hand) is used for the "Don't Walk" sign. However, this doesn't happen in Something Fishy, where only happy tree friend silhouettes are used for the bathroom signs.
- In Water You Wading For, there is a "No Swimming" sign with a human silhouette.
- The characters celebrate many holidays such as Halloween and Christmas.
- In YouTube 101: Subscriptions, humans can be seen when Cuddles was on YouTube.
- A human hand drew the first scene of Dino-Sore Days (outside the fourth wall, so it wouldn't count).
- In Icy You, a wet floor sign was displayed at the end of the episode. It depicted a human instead of a Happy Tree Friend.
- In Boo Do You Think You Are?, a humanoid zombie hand is used as a decoration for the ride.
- In Clause For Concern, Pop pulls out a human-like doll from his sack of toys.
- In Wingin' It, a human face is displayed as a symbol on a barf bag.
- Humans at Wikipedia