The Longest Yarn is a HTFF episode that introduces Carol, the cat with a knack for knitting.
Carol is seen sitting on a log while knitting what appears to be a sock. She is too distracted to notice Thread in front of her, trying to drag himself away from Needle, who is using his wool yet again. Needle calls out to Thread as he fades in the distance, leaving behind only a rather long trail of yarn. Carol, momentarily looking at her, quickly discovers she has run out of yarn. However, she sees Thread's yarn trail and decides to use that to continue her hobby.
Carol begins following the trail as she knits, soon leading her into town. Wooly and Soffie are shown having a conversation that a nearby Baldy finds completely unintelligible. Carol passes by, leading to the wool on Wooly and Soffie's bodies to inexplicably unravel, leaving them naked. Baldy smiles at their predicament and removes his own trousers to join them. Unfortunately, since he is standing over the yarn trail, he gets sliced in half when it Carol stretches it taut.
Just across town there is a circus. Cheerup, who is performing as a clown, blows a balloon spider while Mime balances on a tightrope above. Carol casually passes through the crowd of spectators, still focused on knitting. The tightrope unravels, somehow becoming a part of Carol's yarn, putting Mime in jeopardy. Thinking quickly to save his friend, Cheerup spins a web to form a net. But like the tightrope, it also unwinds. Mime lands on top of Cheerup, killing them both. After Carol makes it past the exit, the tent itself gets unraveled by her yarn.
The scene changes again to show Russell fishing at sea. He casts his line and feels a strong pull. He tries to reel it in, pulling his boat closer to the docks until lethally crashing. It turns out his line was also connected to Carol's yarn. Eventually, Carol passes a well. Giggles, who had been trapped in the well for some time, manages to climb out thanks to the yarn dangling down from the surface. Carol stops to notice a piece of dirt on a portion of the yarn, so she snips it, unknowingly sending Giggles to her doom.Carol continues onward, following the trail to various places like a forest, a desert, a mountaintop and a swamp. She finally reaches a park, where Thread is relaxing under a tree. His peace comes to an end, however, when he sees Carol in front of him, using the last bit of his wool to finish her project, which is revealed to be a huge ball of yarn. Needle, catching up to them, stares at the ball in amazement while Thread covers his exposed parts.
Carol leaps onto her yarn ball to play with it, unwittingly pushing it towards Needle and Thread, crushing them.
- Baldy is split in half by the yarn.
- Mime and Cheerup collide into each other.
- Russell dies when his boat crashes.
- Giggles falls down a well.
- Needle and Thread are crushed by Carol's yarn ball.
- The title is a reference to the film The Longest Yard.
- The plot shares similarities with the SpongeBob SquarePants episode The String.
- Carol caused every death in this episode.