Continuity Errors

A continuity error is defined as any time in a piece of fiction where an event in the plot (whether small or large) contradicts information previously received. It has been stated that Happy Tree Friends relies largely on an absence on plot continuity to function. This allows them to kill any of the characters and still have them available to use in later episodes. However, in addition to characters coming back from the dead and/or miraculously losing major injuries, there are many other cases of continuity errors from episode to episode and even some within the same.

Cuddles

 * In the HTF Break Seize the Day, Cuddles is clearly shown to suffer from photosensitive epilepsy. However, in In a Jam, he is completely unaffected by the flashing lights, even though they give Handy a seizure. (It is possible that Cuddles did not suffer a seizure because he was not focused on the lights, or due to the fact that he only had one eye, as obscuring one eye can lower the risk of seizures.) He was also seen amdist strobe lights in Keepin' it Reel and did not have a seizure (though these might have not been the correct frequency for seizures).

Giggles

 * Giggles has dated several different male characters throughout the series.

Toothy

 * Toothy is presumably allergic to bees, as he gets stung by one in the eye in The Carpal Tunnel of Love, which results in it getting swollen. However, in Aw, Shucks! he encounters with a swarm of bees which sting him numerous times, but Toothy's body does not even swell up a little, which contradicts his "allergy". There are two possible explanations to this last fact: The theory about Toothy's allergy is just a rumor from the show's audience, or the bugs that stung him in Aw, Shucks! are just wasps instead of bees.

Lumpy

 * The size of Lumpy's brain changes many times throughout the entire series. Lumpy's brain is suppose to be small enough to fit inside his small head, but there are some instances of Lumpy having a large brain, like in In a Jam and All Flocked Up.
 * In Snow What? That's What!, Lumpy is shown relaxing shirtless in a hammock without being affected in any way, but in Just Desert, he is dressed in very heavy winter clothing to go hiking in the mountains. Furthermore, in Snow Place to Go, he is shivering in the cold along with everyone else (though it is possible that he can only take the cold for a certain amount of time).
 * In All Flocked Up, Lumpy is unable to climb a tree, so he has to come up with other ways, but in Doggone It, he climbs one effortlessly to escape Whistle. (This could be due to the fact the tree in All Flocked Up was much larger in circumference).
 * In Concrete Solution, Lumpy has blue eyes, but in Wishy Washy, his eyes are green.
 * Lumpy has hoofed feet in Every Litter Bit Hurts, but toed feet in Wipe Out!.
 * In Wingin' It, Lumpy falls out of an airplane and, upon landing, has his leg bones push out his shoulders, but survives for the time being. However, in All Flocked Up, he falls out of a tree and splatters upon landing.
 * Lumpy's wealth throughout the series varies. In most episodes, he is shown to live in a trashy trailer and most likely unemployed in the majority of those episodes, but in several episodes such as Aw Shucks! and Peas in a Pod, he seems to have a very successful life and even owning a large house and having high paying jobs.

Handy

 * Handy's arms are cut off at the elbow in The Wrong Side of the Tracks, but they are cut off at the wrist in House Warming, Concrete Solution, From Hero to Eternity, and Double Whammy Part I.
 * Handy's hardhat can also come to debate. It is shown to be able to withstand objects such as glass (Ipso Fatso) and even car tires (Pet Peeve), yet offers no protection against objects like a lawnmower (A Sight for Sore Eyes) or helicopter blades (Who's to Flame?).
 * Handy has his ears visible in Blind Date when his hat went up for a brief second. However, the same happened in Pet Peeve, but it seems he hasn't ears at all which is very odd since he is a beaver (like Toothy who has also ears).

Nutty

 * In Concrete Solution, Nutty has a bowl of fruit on top of his fridge, but in Chew Said a Mouthful, he is shown to hate fruit (Debatable, as it could be for decoration).
 * In A Change of Heart, Nutty is seen waiting in line in a butcher shop, despite how he strictly only eats sugar (Debatable, as Nutty might have either wanted to try something outside of sugar, like meat, or the writers just needed another character to fill in some space).

Sniffles

 * A glaring example would be how the length of his snout changes throughout the series, starting out very long and later becoming a lot shorter.
 * However, this was done as a design change to make him cuter.
 * The length of Sniffles' tongue also varies. In Crazy Ant-ics and Tongue in Cheek, it is shown to be very long, but in Tongue Twister Trouble, he runs out of tongue while sliding much sooner.
 * Sniffles seems to have a second mouth (like a moray eel) near his skull. However, in some other episodes, he reverts to only having one (the one existing being the snout.)

Flaky

 * In From A to Zoo, Flaky is clearly shown to be afraid of chicks, but in Take a Hike, she saves an eaglet without any sign of fear. It is possible, however, that she is only afraid of certain kinds of birds.
 * Similarly, in both Ski Ya, Wouldn't Wanna Be Ya! and Mime to Five, Flaky is very clearly shown to suffer from acrophobia (fear of heights). However, once again in Take a Hike, she is not afraid to climb the tree to return the eaglet to its nest, and in Ski Patrol, she seems comfortable and happy on a ski-lift. (However, in Mime to Five, it could have been performance anxiety.)
 * Handy is shown teaching Flaky how to drive in Easy Comb, Easy Go, even though she is seen driving alone in Concrete Solution, which premiered earlier.
 * In Ski Ya, Wouldn't Wanna Be Ya!, Flaky is afraid of skiing even extremely small "hills", but in Ski Patrol, she seems perfectly happy going skiing.
 * Flaky's conception on Flippy varies throughout the series. Flaky is also shown to be relatively calm about Flippy as she is seen giving him a cake knife, most likely aware that he has a tendency to flip out in Party Animal. However in Without a Hitch, she immediately freaks out about Flippy pulling out a knife to save her.

The Mole

 * In Stealing the Spotlight, it is implied that The Mole cannot feel pain, as he does not notice that his thumb is on fire. However, in Double Whammy Part II, he notices when he cuts his foot on a piece of glass. (It is possible that he can only feel pain in certain parts of his body.)
 * His hearing in episodes can vary from good, to average, to almost completely deaf.

Russell

 * In Sea What I Found, he needs to wear scuba gear, but in Off the Hook and Sea of Love, he is shown without it. (It is possible that it is simply a matter of depth and/or time difference.)
 * Sea What I Found shows him to be able to take off his peglegs much like shoes, but in You're Kraken Me Up and Idol Curiosity, they do not come off when pulled on.

Cro-Marmot

 * In Wipe Out! and Swelter Skelter, Cro-Marmot is shown to have very powerful freezing abilities. However, in From Hero to Eternity, he is seen floating in the flood without having any effect on the water and later on, in By The Seat Of Your Pants, he enters a swimming competition. However, the water may have been moving too fast in the first example, and he is never seen entering the water in the second.

Flippy/Fliqpy

 * When flipped out, his eyes vary from yellow, green, blue in Remains to be Seen, any variation of the first two, and even staying normal pac-man black in his debut. (Though the blue eye variation is most likely a goof.)
 * In Double Whammy Part I, it is revealed that if you dump water on Fliqpy, he will flip back to Good Flippy. However, in By The Seat Of Your Pants, Fliqpy goes into the pool to chase after Lumpy without flipping back. (Debatable as this could be due to the fact that in Double Whammy Part I, him being splashed with water was a surprise to him, while in By The Seat Of Your Pants, he was fully expecting the water.)
 * Despite being cured at the end of Double Whammy Part 2 (Autopsy Turvy), he still flips out in the future episodes of the show.

Splendid

 * Splendid's vulnerability often comes into question. Despite being able to survive the moon hitting the planet in Mirror Mirror, he is confirmed to have died in an explosion in Class Act.

Mr. Pickels

 * In both animate and inanimate form, the size of Mr. Pickels repeatedly changes, sometimes even in the same episode.

Non-Character

 * The time period of the show constantly varies to complete impossibility with the different types of technology shown.
 * Many episodes show a beach in or extremely close to town. However, Who's to Flame? shows an overview of the town depicting it as completely land-locked.