Since you're good with episodes, I think give you a episode idea named Emotion Cats (Starring: Chef Meow, Featuring: Fatty, Sniffles). After Sniffles lose his emotion clone machine, Chef Meow finds it and accidentally creates five clones of him, who are his emotions (joy, sadness, disgust, anger, and fear) whose colors and personalities are similar to the Disney film Inside Out.
Hi, I'm new here, and I like your characters, spin-offs, and episodes, and I want give you these ideas: (if you want)
Here the character concepts:
An unnamed green male tazmanian devil character, who is very crazy, and is very destrutive, and sometimes ends up accidetally killing any character (except characters who make fun of him). Based on the Tazmanian Devil from Looney Tunes. This could be your second tazmanian devil character, along with Tazzy, except with the fact that he is a HTFF character, while Tazzy is a AOF character.
Marlina, Dumby, and Grump - Marlina & Dumby are a purple female cat and a green male dog who are best friends, and are very stupid which can lead to their deaths. Grump is a red male bear who is an short-tempered (hence his name) character, he dislike both Marlina and Dumby, and always tries to getting away from them, but it can lead to his deaths. They are based on SpongeBob SquarePants, Patrick Star, and Squidward Tentacles.
Jossephina, Peter, Charlotte, and Basil - An group of four sibling bears, Jossephina (the oldest and angriest sister), Peter and Charlotte (the middle siblings), and Basil (the youngest and goofball brother). They are criminals who are convicts, hence their prison jumpsuits. In each of their starring roles, they run away often from prison, to commit their crimes, but they always end up returning to prison, after being defeated by any other character, only to the ineptitude of the police allow them to escape again in the following episode. At the end of each episode in which they star, they are fighting in prison in a comic way. Based on the Dalton Brothers from the French comic strip Lucky Luke.
Now the spin-off idea:
Happy Tree Friends: Unfortunate Tree Island - A parody of well-krown reality game shows like Survivor, Fear Factor, and the animated Total Drama Island. It about 30 HTF (both canon and fanon) characters (all dvided into two teams) compete at an island named Unfortunate Tree Island in order to win $100. Lumpy is the host. (you can decide the characters).
Here the episodes requests:
Puppet and Kisses (Starring: Nuppet and Quist, the Mouse Family and Spike) - Spike and Quist fall to love shortly after Spike saving Quist from being crushed by a elevator, however it make Nuppet gets jelously of Spike, and joins forces with the Mouse Family who gets jelously of Quist.
Water Woodpeckers (Starring: Pecky, Peckia, Commy, Maddie, Featuring: Cole, Peckins) - Pecky and Peckia try to bath Peckins, but Commy steal the water for make a water park, however, Pecky and Peckia make a constest aganist both Commy and Maddie in every attraction in the park, they [Commy and Maddie] try to make traps, but fail. At the end of the episode, Cole steal all the water for make his own water park, and he forbids both Commy and Maddie from entering the park, as an act of revenge for everything that Commy forced Cole to make. (this could one of the many episodes which Cole takes revenge aganist Commy)
Scrams and Loves (Starring: Milton and Mafalda, Swindler, Sorcery) - After begin framed by one of Milton and Mafalda's scrams, Sorcery takes revenge and with his magic makes Mafalda falls in Swindler, who hates her, due to the clasic mouse/rat-cat rivality. Milton, thinking Mafalda is insane, tries to help Swindler, despite being rivals.
Gone in 30 Minutes (Starring: Naz, Featuring: Lumpy) - Naz tries to deliver a pizza to Lumpy's hotel, but she goes to have troubles in the process.
If you're not too busy, could you make an image for Double, Double, Toilet and Trouble and Rotisserie (that headless chicken character idea I had long ago for that contest)? Rotisserie doesn't have a page yet, but I'll make it soon.
Rotisserie's a raw chicken with bone and cartilage where its feet should be. As Rotisserie is a dead chicken, you can't tell its gender. Rotisserie's wings are on the side of its and has a gaping hole underneath Rotisserie and where its head should be.