One night, the Purple Dragons is preparing to break into a museum. Meanwhile, on the rooftops above them, Donatello and Casey Jones are showing off their athletic capability to each other while attempting to impress April. April doesn't seem to be thrilled about this and, when Casey decides to give April a 'peace hug', Donnie directs his attention toward the Purple Dragon robbery about to take place down below. The trio quickly follows the Purple Dragons into the museum and they engage the gang members. The Purple Dragons try to steal all kinds of things for Steranko, but all of their attempts are blocked. However, the criminals are able to make their escape because Donnie and Casey argue about one another's attempts to impress April. In an alleyway, Fong (the Purple Dragon leader) reveals to his partners that he was able to steal a small, ancient-looking dagger. Fong then removes the blade's sheath, allowing a mysterious figure to come out of the blade and he introduces himself as 'Ho Chan', ordering the Purple Dragons to bow down before him.
The Purple Dragons start to wonder if the thing that's speaking to them is a ghost, only for the 'man' to explain that he was a supreme master of one of the first Martial Arts to ever exist and an art that, if performed correctly, appears similar to magic. Ho Chan explains that his spirit was trapped inside the dagger and he offers to give the three Purple Dragons unparalleled power if they agree to help him take over the world. The Purple Dragons agree to this and are given inscrutable storm powers (Fong gets lightning, Tsoi gets wind and Sid gets thunder), which they demonstrate. Then, Ho Chan commands them to find him a 'lair of opulent beauty' and the Purple Dragons lead him back to their own hideout (an abandoned Tattoo Parlor). Ho Chan doesn't like the condition of the inside of the building, but says that it will have to do...
Meanwhile, in the underground lair, the Turtles are wondering about Serpent Karai's whereabouts when Donnie tells his brothers that their search for Karai has been going on for at least a week and that they'll most likely never find her. Leo and Raph point out that Splinter would disagree and that he hasn't been the same ever since his daughter's mutation. Raph tells his brothers that, to get better results in their search for Karai, they'll need Casey and April (who are at the ice rink) to help them.
Back at the Purple Dragon's hideout, Ho Chan is once again perturbed by his surroundings. Meanwhile, the Purple Dragons start to use their powers on one another, but Ho Chan commands them to stop and tells them that he has a very important task for them to do. He tells the Purple Dragons to go out and capture a girl that has a power within her that can restore him to his past life as a human. That girl turns out to be… April!
Over at the ice rink, April and Irma are having quite a lot of trouble keeping their balance on the ice, but Casey remarks that April shouldn't be upset, as Casey has been practicing ice-skating for many years. Before long, the Purple Dragons force their way into the ice rink through the ceiling, and Casey wonders why they're here if they just got their butts kicked. Casey boldly squares off with the powerful gang, not knowing they are much more of a challenge. He is quickly defeated by the gangs' powers. When Casey has been hit down, the Purple Dragons seize both April and Irma and, with that, they become airborne and fly out of the hole in the ceiling with April and Irma in their arms.
The Purple Dragons bring April and Irma back to their headquarters, where Ho Chan looks April over and tells her that she has power in her that has barely been tapped, which Ho Chan intends to take. He then walks over to Irma and takes off her glasses, informing her that she has power in her as well, although Ho Chan doesn't understand it... yet. Then, April takes out her tessen and breaks away from the Purple Dragon that's holding her. She then encourages Irma to break free as well, but, when Irma pointlessly kicks at Ho Chan, her foot passes right through his semitransparent body and she asks him if he's some kind of ghost. Ho Chan tells her that he's been cursed without flesh for 2,000 years and he then restrains both her and April with glowing ropes, informing them that a ritual is about to start...
Meanwhile, the Turtles have arrived at the ice rink and Casey has already told them about what happened. Donnie immediately chastises Casey for allowing April to get taken away, but Casey replies that the Purple Dragons have powers. Donnie adamantly refuses to think that the Purple Dragons are powerful, firmly believing that they are only a gang of third class wannabes. Raph starts to think that Casey might be right, but, even so, they'll need to search for April and Irma and rescue them both. Casey humorously asks if they can save April and leave Irma with the Purple Dragons, but every one ignores him and rushes out.
The team soon arrives at the Purple Dragons' headquarters and Raph questions how tough the Purple Dragons could possibly get. Casey then rides up on his bicycle and attempts to hit one of the Purple Dragons, only for the Purple Dragon to knock him to the ground with a blast of wind. Raph then finds the answer to his question...The three Purple Dragons then attack with their mystical powers, but the Turtles defeat them after a little while. Ho Chan then appears and, having just seen the Turtles fight, he makes Leo, Raph and Mikey become his minions after revoking the powers from the Purple Dragons and giving them to the Turtles. Ho Chan then starts to attack the Purple Dragons, making them cower in fear and run away, while Casey and Donnie are in shock that the other turtles are now mind-controlled. Casey and Donnie make haste and board the Shellraiser to make a retreat, while Leo, Raph and Mikey pursue them. Casey is able to drive the Shell-Raiser into an alley way, where Leo, Mikey and Raph fail to spot them. Donnie and Casey then find the Purple Dragons hiding underneath the Shellraiser and Casey pushes them against the side of a building, interrogating them about their connection with the ghostly man. Fong (the Purple Dragon leader) tells him that the man promised them great power and gave it to them, though he had the power to control them all along. Fong then reveals the man's name: Ho Chan.
Back in the Sewer Lair, Casey and Donnie decide to research Ho Chan on Donnie's laptop. They find out that Ho Chan is actually an ancient sorcerer that dates back to the Shang Dynasty. They then read that the only plausible way to defeat Ho Chan would be to use the mystic dagger against him, which is what the Purple Dragons stole from the museum. Casey then asks Donnie what they should do about his mind-controlled brothers. Donnie replies that nothing can get them out of their super-hypnotic state, but Casey disagrees, as an advertisement for free Pizza pops up.
Donnie and Casey drive the Shellraiser back to the Purple Dragons' hideout, but Leo, Raph and Mikey quickly spot them and descend from the clouds. The three brothers work together to create an enormous gale of wind that quickly sucks Casey and Donnie up into it. While Casey is quickly defeated by Leo and blown down to the street, Donnie remains in the gale of wind and bravely tries to fight off his brothers, but he is defeated by them as well. Casey then reveals his and Donnie's plan, which is to distract Leo, Raph and Mikey with Pizzas! Casey fires several pizzas out of the Manhole Cover Cannon in the Shell-Raiser and this entices the Turtles long enough for Casey and Donnie to go behind their backs and break into the Purple Dragons' headquarters. Meanwhile, inside, Ho Chan has nearly finished the process of draining the 'essence' from April and Irma that can make him become human. Casey asks Donnie if they should just whack Ho Chan while his eyes are closed, but it turns out that this plan won't work, as Ho Chan is listening to his every word. Ho Chan mentally tries to call the other turtles to his aid, but the three are still preoccupied with eating the Pizzas out in the street. Casey then leaps at Ho Chan and tries to attack him, but misses. Ho Chan mystically extracts some of the essence from April and starts to become human as he outwits Donnie and Casey in battle. Donnie is able to recover the mystic dagger from the floor and, just when he and Casey are about to get crushed by Chan's gigantic hands, Donnie throws it at Ho Chan's face and Ho Chan catches it. Then, April jumps down, grabs the mystic dagger from his hands and thrusts it into his torso, after which he returns to the inside of the dagger and Donnie covers the dagger with it's sheath. Leo, Raph and Mikey then enter and are no longer under the influence of Ho Chan, as he has been defeated. An exhausted Irma then rejoins Casey and April, and April convinces her that she has a bad bump on her head and that whatever she saw was only a nightmare...
Later, Donnie and his brothers drive down to the docks during sunset and Donnie throws the mystic dagger (with Ho Chan trapped inside of it) into the ocean and it sinks into the depths, while Ho Chan vows that he would return.
"Michelangelo: Those guys are like a level one boss battle, who cares about the Purple Dragons anyway?"
"Ho Chan: Moron, I grant you the power of lightning.
Stupid idiot, you'll become thunder.
And numbskull, you are wind!"
"Ho Chan: Now, go find me a lair of opulent beauty, worthy of my divine powers!
Whataheck is that?
Well, it will serve."
"Leonardo: I dont like the looks of this.
Michelangelo: I like the looks of those hats, they're awesome!"
"Ho Chan: It is said the great turtle helped the god Pangu to create the world."
"Fong: But master, why?
Ho Chan: Because you're losers."
"Michelangelo: Where do snakes hang out? Swamps, deserts, pizzarias, ice cream parlors, arcades..."
Ho Chan is a parody of David Lo-Pan, an evil sorcerer and the central antagonist of the film, played by James Hong, who also voices Chan in the episode. Both characters are defeated with a dagger at the end.
Ho Chan says Irma also may have powers, Irma has green eyes and in the film only a girl with green eyes could make Lo Pan mortal again.
The Purple Dragons represent the film's Chinese street gang "Lords of Death", as well as "The Three Storms" with their straw hats and glowing eyes.
Kevin Eastman talked in an interview about how "Big Trouble in Little China" influenced the personalities of Donatello and Casey Jones in the original comics. By coincidence this episodes's main plot revolves around Donnie and Casey.
Ho Chan's line "It's all in the reflexes." is one of the film main character's best known catchphrases.
Ho Chan says "I see a girl with red hair and a yellow jumpsuit, no, it's just a t-shirt." as a reference to 80's April outfit.
Sid yells "Shoryuken!" as he attacks Michelangelo, the same expression used while performing a Dragon Punch special move in the Street Fighter video game series.
Ho Chan threatens to banish the Purple Dragons to the Abyss of Infinite Morons, which is an analogue of the early English-dubbed DragonBall Z version of Hell, "Home For Infinite Losers".
When Leo electrocuted Casey it was shown he has a metal plate on his skull.