SpongeBob is in his kitchen, karate-chopping a pineapple to look like Gary. He puts it on the floor, so Gary is eye-level with it. It attracts flies and one flies into SpongeBob's mouth and he begins to choke. Patrick walks in and asks for some cheese before realizing SpongeBob is choking. Once it becomes clear to him, he punches SpongeBob. SpongeBob flies across the room and lands against the wall and the fly leaves his mouth. He offers anything in return and gives Patrick the cheese.
While he's watching SpongeBob practice his karate exercises, Patrick asks his best friend to teach him karate. SpongeBob's a little skeptical, but ultimately agrees since that was part of the deal. He tries to teach Patrick the "reverse whirlpool," and then how to fly into a brick wall and destroy it. Patrick succeeds in this but ends up unable to stop flying and destroys a lemonade stand. Next, SpongeBob tries to teach Patrick a move where he spins around on one foot. Patrick then starts spinning uncontrollably. SpongeBob gives up, and Patrick perfectly karate-chops a cinder block in half out of anger. He chops a steel sword and a boat as practice and then almost chops Baby Rechid. SpongeBob stops and warns him not to chop any living organisms or their property. He reminds him that "with power comes responsibility," but has to go to work and leaves Patrick, who starts chopping everything from arcade games to spinach.
A man runs into the Krusty Krab screaming that there is a "mad chopper" on the loose, and SpongeBob, knowing the man is referring to Patrick, sets off to stop his friend. Meanwhile, Patrick is in an ice-cream shop. He is buying a cone stacked high with every flavor they have. He owes the ice cream man over eighty dollars but tries to trade him for a lollipop. The ice cream man refuses and threatens to call the cops when Patrick chops the glass, cracking it, and tips the ice cream into his mouth while the ice cream man holds onto the money from the tip jar. The manager yells at the ice cream man for holding the money in the tip jar. Patrick gains considerable weight, and no longer fits through the door. He chops it, and exits. SpongeBob comes and tells Patrick to stop destroying Bikini Bottom, but by that time, Patrick's arm cannot stop chopping. He eventually makes his way to the Barg'N-Mart and destroys the structure and crushes SpongeBob. He finds a pack of kitchen sponges, and believes that this is SpongeBob's carcass. He becomes very mad at himself and rips off his own hand. The real SpongeBob, who was trapped under a pile of rubble, wakes up and Patrick grows his hand back, swearing never to use karate again.
Patrick then badly rebuilds the Barg'N-Mart. Patrick is then shown karate chopping a shopping cart, leaving SpongeBob confused. Another Patrick then appears, and the original-Patrick explains that in addition to sea stars being able to regenerate limbs, the limbs that fall off are able to regenerate bodies. The two Patricks then laugh as the Barg'N-Mart gets destroyed again, and the episode ends.
Like a real-life starfish, Patrick's arm grows back. Patrick's dismembered arm growing into another Patrick is also accurate: if a starfish's limb is cut off and has enough of the original body attached to it, it can grow an entirely body.
Although SpongeBob told him not to chop any lifeforms, he has never chopped any lifeforms, but chopped property instead.
The way that only SpongeBob's legs were seen when he was crushed is similar to the 1939 film The Wizard of Oz.
When Patrick slices the cinder block in half, the halves look similar to the brick blocks from the Super Mario series.
When SpongeBob told Patrick about power and responsibility, he said: "With power, comes responsibility.," as Voltaire, a famous French philosopher once did. It is also a famous quote from "Spider-Man." This is also referenced in the episode "Rule of Dumb."
Patrick saying "Oh, yeah!" and bursting through a brick wall might be a reference to vintage Kool-Aid commercials where the Kool-Aid Man bursts through a wall and yells "Oh, yeah!"
When Patrick chops through the Krusty Krab doors, the yellow handles do not appear on the floor.
When SpongeBob says "Patrick!" while riding his unicycle, his mouth does not move while he's talking.
Although it is revealed in "You Don't Know Sponge" that Patrick's dominant hand is left, he chops with his right hand the majority of the time.
When Patrick cuts the block of cinder, SpongeBob's hand is larger than usual.
Patrick can smell in this episode (the scene after the ice cream shop), whereas in "No Nose Knows," Patrick did not have a nose and was unable to smell.
When Patrick heads to the Barg'N-Mart, SpongeBob says "Tritains tunic!" in his normal voice. However, when it shows the Barg'N-Mart, he says "He's heading straight for the Barg'N-Mart!" in a deeper voice.
When Patrick enters the Barg'N-Mart, he says, "Not the muffin display!" before chopping a tray full of pastries. However, considering that they are topped with pink frosting, the "muffins" are more likely cupcakes.