Banned In Russia: The show was taken off the air from Russian TV channel 2×2 for "promoting violence and brutality".
Creator Backlash: The crew, apparently, did not like Gems the Breaks but for what reason is unspecified. And, on an ask account on Reddit, Warran Graff was displeased on how Home Is Where The Hurt Is turned out.
Enforced Method Acting: In "Shard at Work", Warren Graff choked himself with water while recording the scene where Handy gets a fish bowl stuck on his head.
Missing Episode: Several "irregular" episodes can't be found on Mondo Media's website. Among them are "Dino-Sore Days" (a sketch featuring a non-ice-encased Cro-Marmot), "Intimate Spotlight" (an "interview" with Cro-Marmot), Cuddles's "Smoochie" episode, and a Christmas episode titled "We Wish You".
Giggles, Petunia and Cub have always shared a voice actor, though the role has been replaced twice: first Dana Belben, then Ellenn Connell, now Lori Jee.
David Winn replaced Rhode Montijo as both Lumpy and Splendid when Rhode left the show. Similarly, Kenn Navarro replaced Mark Giambruno as both Lifty and Shifty (although Giambruno's laughs were sampled in at least one episode) and Francis Carr replaced Jeff Biancalana as Russell.
Kenn Navarro voiced Handy in "A Hole Lotta Love" because Warren Graff was unavailable.
According to the Happy Tree Friends wiki, Kenn Navarro also voiced Toothy in Keepin' It Reel.
Subverted with Pop; Aubrey Ankrum's voice has been sampled since he left the show. Ankrum is also sampled for evil Flippy, but Kenn took over voicing good Flippy.
There hasn't been a single episode since early 2014, though this is because of the movie being worked on.
Screwed by the Lawyers: Well, They created a special warning video for Youtube users about the danger of Copyright. Users would be forced to watch it when they get a full on Copyright strike on Youtube.
Giggles, Petunia and Cub have always had the same voice actor, although the role has changed twice.
Lumpy and Splendid have always shared a voice actor, even when Montijo left the show.
Lifty, Shifty, Cuddles and good Flippy are all voiced by Kenn Navarro, although initially, Kenn only did Cuddles' voice.
Toothy and Handy have always had the same voice actor. Strangely enough, they've never interacted.
What Could Have Been: A commentary in the First Blood DVD revealed various concepts. That also includes prototypes and unused concepts.
A few rejected characters:
Pranky the bear.
Cookie the chef sloth.
An unnamed centaur character.
A fugitive character whose head is phallic instead of round. (species is not clear)
A cyborg bear, whose one side of his body is mechanical.
Mafia Doctor the deer, possibly based on quack doctors. He has one of his cheeks bandaged, has a broken right arm, has his feet stuck in concrete blocks, and wields a saw.
An unnamed monkey.
Penny the princess/queen bear.
Bunny Bumpkin the, well, bum.
An unnamed bear character in a warrior-like outfit.
An unnamed possum character who is supposed to be Mole's arch-rival.
An unnamed female possum character with a flower on her head and small (possibly) possum plushies stuck on her body.
Swami the skunk.
Meat Face, a character whose head is covered with a bag.
Skizzy the tall, skinny squirrel.
An unnamed platypus character in a strait jacket.
Princess the rabbit.
Prototypes involving existing characters include: Lumpy being a bear instead of a dinosaur in an early sketch about the pilot episode, Shifty being a squirrel, Pop only donning his hat and having his smoking pipe, Flippy having bandages covering his injuries and having a broken arm, Russell with a long beard, Cub being named Fuzzy, Sniffles being a squirrel, and Flaky having ears and being named Corky.
Pop was originally going to be in Happy Trails Part 2, but the writers didn't like the idea of him appearing without Cub or murdering Flaky in cold blood. They instead opted for Flippy, which makes it much easier since they were (at the time) voiced by the same person.