Sometimes in Happy Tree Friends, something will happen that implies the characters are aware of being fictional characters in a cartoon. This is known as breaking the Fourth Wall. The term "fourth wall" originated from plays in theaters, when actors would look at the audience, talk to them, or do anything else that involved the audience. Because the stage would generally have a wall at the back and both sides, this concept involves the actors becoming involved with the audience who are at the front, which can be considered an invisible wall, making it the fourth one. The Fourth Wall is most often broken in smoochies, but has also been broken in TV episodes.
- Pet Smoochie: Cuddles waves and says hello to the viewer(s).
- Easter Smoochie: Toothy waves and says hello to the viewer(s).
- Valentine Smoochie: Giggles blows a kiss at the viewer(s).
- Summer Smoochie: One of Petunia's deaths involves her being crushed by a hose pipe against the screen, and the screen cracks before she explodes.
- Baseball Smoochie: Flaky waves and chuckles nervously to the viewer(s).
- BBQ Smoochie: Pop waves his hat and says "Hello there!".
- Olympic Smoochie: Mime throws a heavy metal ball which bounces off the side of the screen and smashes into his face.
- Halloween Smoochie: Disco Bear dances for the viewer(s).
- Party Smoochie: Nutty's car bumps into the sides of the screen.
- Science Smoochie: Sniffles' guts fill up the screen and eventually dies in the oversized guts, similar to Petunia's death from her Smoochie.
In TV Episodes
- The Wrong Side of the Tracks: Lumpy looks at the viewer and shrugs after finding Nutty's cotton candy near the rollercoaster.
- And the Kitchen Sink: When Pop's car lands in the water, it makes a big splash, it can be seen that there is water on the screen sliding and dripping down.
- Party Animal: Cuddles' blood stars spreading on the screen, and at the end, the iris closes on Flippy's mouth, cutting off his lips.
- Wipe Out: When a wave splashes on Flaky and Cuddles, it can be seen that there is water on the screen sliding and dripping down. Also, Lumpy grins at the viewer after his "hair" flies off.
- As You Wish: After Mime makes his balloon animal, he looks at the viewer.
- Take a Hike: They hum the HTF theme song at the start of the episode (they also do this in From A to Zoo and the internet episodes This is your Knife and Happy Trails) (Debatable, because they could also act as a song written by a Happy Tree Friend in the series).
- Wingin' It: Flaky stares at the viewer, when she pops the raft near the end.
- Blast from the Past: Cuddles yells, "Oh my God, I'm gonna die! Not this old death again!" This implies that he knew he died in Spin Fun Knowin' Ya.
- Mime to Five: Flaky breaks the fourth wall by looking at the viewers before her demise.
- A Hole Lotta Love: After the drill machine breaks, Sniffles' and Pop's faces smoosh in front of what appears to be the TV screen.
- Every Litter Bit Hurts: At the end of the episode, when Giggles' heart drops out of The Mole's bag, blood from the heart squirts outside the closing iris.
- Aw Shucks!: Flaky breaks the fourth wall by looking at the viewers and laughing nervously before her death. (Although, she could of been looking at the target when the popcorn misses it)
- Easy Comb, Easy Go: In the beginning of the episode, Disco Bear waves at the camera and says, "Hey!"
- Wishy Washy: When Petunia got out a potato peeler she looked at the viewer before killing herself.
- Double Whammy: After Flippy realized he killed Nutty, he looked at the viewer.
In Internet Episodes/Games
- Milk Pong: When Handy and The Mole send Lumpy through a log-cutting machine, Handy looks at the audience in shock/horror (debatable).
- A Sucker for Love: At the beginning of the episode, Pop smiles at the camera.
- Stayin' Alive: At the end, Disco Bear is dancing for the audience and gives a growl to the audience.
- A Hard Act to Swallow: An ant re-opens the closing iris and cheers at the viewer.
- Just Desert Blurb, a Blurb reading "Blurb placed for your protection!" is placed over Lumpy's crotch.
- Water You Wading For: Flaky is the first to break the fourth wall by looking at the camera after witnessing her friend's death and nervously laughing.
- I Nub You: Petunia growls at the viewer after she realizes she can't pick up a bowling ball.
- Many episodes in which Handy appears: Handy growls at the viewer after realizing taht whatever task he's trying to do requires hands.