In this episode, The Powerpuff Girls decide that they all three are not enough to fight crime, so they needed another one.
Blossom opened up the book on the Ingredients to make a Powerpuff Girl. They were supposed to put in Sugar, Spice, and Everything Nice, and finally pour in Chemical X. Instead, Bubbles found Artificial Sweetener and Buttercup found Dirt, Twigs, and Stuff. For Everything Nice, Bubbles and Buttercup found some stuff that was of course, none of the Everything Nice that Professor Utonium used to create those three Powerpuff Girls. Blossom told Bubbles to pour in Chemical X, and NOT to drop it in, but Bubbles accidentally dropped in Chemical X.
Then, there came a big and strong Powerpuff Girl with brown hair, purple eyes, and dressed up in purple. The three Powerpuff Girls were choosing a name, and finally, Bubbles picked the name, "Bunny", and they all decided it was her name.
Bunny was supposed to fight crime. However, Bunny did free prisoners that were NOT allowed to escape from Jail. The Powerpuff Girls caught Bunny freeing prisoners, and told her to fight crime.
In the end, Bunny finally exploded.
In this episode, Buttercup is obsessed with her blanket.
The first day, The Powerpuff Girls fight human criminals, The next day, they fight an evil robot. The next day, The Powerpuff Girls fight a snip-snip monster.
The next day, Buttercup is in the closet with her blanket saying to herself, "I am a good fighter." When Buttercup exits the closet, she lies to Blossom and Bubbles saying that she is practicing her spelling. Buttercup refuses to tell them what is behind her back. When they go to another room, Blossom grabs the blanket from Buttercup and asks her what it is, while Bubbles keeps ahold of Buttercup. Buttercup tells them it's her blanket. Buttercup decided that she needed it to fight.
The next day, Buttercup is missing her blanket. Buttercup checks through the house, making a terrible mess. First, she checks in The Powerpuff Girls' room, then the closet of the same room, then in the closet of Professor Utonium's room, then in the laundry room, then in the kitchen, and then she goes to the counter and starts crying. Blossom and Bubbles take her out to fight crime, and she cries even more.
When they fight crime, Buttercup pretends to fight, until the monster attacks her severely. Blossom finds a fake blanket and gives it to Buttercup. Then, Buttercup fights the monster to his death.
When The Powerpuff Girls return home, Blossom goes over to Buttercup and tells her the truth that it was a fake blanket she found to get her through the fight. Then, Buttercup re-checks through the house for her real blanket, after she learns from Blossom in what Blossom found, was not her real blanket. Then, Professor Utonium comes to The Powerpuff Girls' room with a load of clean laundry, including the blanket that Buttercup was obsessed with. Buttercup picks up the blanket, hugs it, and then she overcomes the blanket and gives it to Professor Utonium.