"Party Animal" is episode number 2.1 of the Happy Tree Friends TV Series.
At the hospital, Dr. Lumpy cures her and tells her she's allergic to any kinds of nuts and to never eat another nut or else. Mime is riding on his unicycle and he offers them some peanuts, but Flaky and Lumpy are frightened by the looks of them. So, he slaps Mime's peanut bag and Mime cries in his mime way.
Back at the house, Flaky, Cuddles, Toothy, Nutty, The Mole, Mime, and Sniffles decorate the place for someone special. As they finished each task, Flaky sees someone coming towards the house and tells everyone to be quiet and The Mole turns off the light. That similar sillouette enters the house and when the lights are turned back on and everyone shouts "SURPRISE!", and since it's his birthday, Flippy felt that he was traumatized, but luckily, he's relieved afterwards. Everybody sings "O He's a Jolly Good Fellow" as Flaky brings a birthday cake towards Flippy, and he's really happy that everyone remembered his birthday. He makes a wish and blows out the candles. Flaky insists that Flippy should cut out the cake, but as he sees a cake cutter and about to flip out, he snaps out of it instantly, and he happily cuts the cake.
Meanwhile, Nutty fills the fruit punch with too much sugar and after he takes one drop of sugared punch, he gets a really crazy sugar rush and spins like a tornado. He blows some peanuts out of Mime's hands and throws them in Flaky's mouth as she's about to eat the first slice of cake. She gets the same allergies as she did last time, and pops the balloons with her quills, and hearing the sounds like shooting guns from the Vietnam War makes Flippy flip out.
First he attacks Toothy by cutting part of his face with a cake cutter. He stares at Cuddles as he ties the balloons around his neck and he lets go of them and the fan pops the balloons and it chops Cuddles into pieces. Next, Flippy carves Nutty like an apple and he stops spinning and falls dead. Mime is looking for peanuts(like he did twice) in the blender and Flippy plugs in the cord and Mime's hand is chopped and Flippy pushes him in the blender and gets grinded into the bloody mush.
Sniffles saw everything had happened, and he hides in the water barrel. Flippy searches for more victims to kill. Suddenly, he sees Sniffles' trunk in the barrel and puts the lid in it, trying to drown Sniffles(who tries to get out of there), putting knives in the barrel, taking it outside and roll it down the hill, and the barrel gets hit and Sniffles get cut by the sharp utensils.
Flaky, still bloated, needs to get out of the Mole's way because he was in the middle of a game called "Pin the Tail on the Donkey". As he was about to put it in the picture, he pops Flaky's eye, she explodes, impaling the Mole and that sound gets Flippy back to his normal sane state. He doesn't remember how it happened. He's drinking the punch as he agrees that this is the best birthday ever. But his face breaks out in a rash and his lips gets swollen and he learns that he's allergic to Mime. The episode ends as Flippys lips get cut by the ending iris.
2. Flippy ties Cuddles to a lot of balloons, letting them go under a ceiling fan, which chops Cuddles into pieces.
3. Flippy carves off Nutty's skin while he's spinning around.
4. While Mime's hand is in the blender, Flippy plugs it in, which chops Mime's hand. Flippy later pushes Mime in the blender.
5. Flippy pushes the barrel Sniffles was hiding in down a hill when it was full of knives.
6. Flaky and the Mole are killed when the Mole pops Flaky, and her quills stab the Mole and pin him to the wall.