The episode starts with Gumball and Darwin clinging onto Nicole's ankles and begging for karate lessons. After Nicole reminds the two of numerous activities they have tried and given up, the boys promise not to quit martial arts after the first lesson and Nicole buys them uniforms. They then talk about how powerful they look, thinking themselves as fierce as a "sharkbeargator." They then make a pact to never remove their gis.
Afterwards, the two mimic karate moves, breaking objects around their house and at the bus stop. At their school, their classmates laugh at the two when they show off; the two remaining completely oblivious to the children's mockery. Nicole notices their classmates' ridicule and tells Gumball and Darwin to get in the car to go home, but Gumball talks to Penny first (she is visibly lost for words). In the car, Nicole tries to convince the boys that the students are bullying them, but they deny her claims and say that they are just laughing with them and even dubbed them "the Karate Wieners," unaware of what the name means and thinking of it as a mispronunciation of "Karate Winners."
When the boys arrive home, they watch Richard play Suburban Karate Master, and hear him wish that he could kick people like that in real life. He then compliments their gis and asks the two if they have a spare. The two say that they do not and note that Richard is not responsible enough to do so, either. The boys go outside and lip-synch a motivational song called "The Inner Warrior," while doing an air guitar. Nicole tries to explain the risk of the boys wearing the costumes to school but Richard ignores Nicole and joins the boys in lip-synching. Nicole then worries about how the costumes will ruin their lives, never gaining girlfriends or jobs, and still living at the house realizing that they have wasted their lives, so she decides to take action.
Nicole walks into the boys' room and sees them on the computer. They explain that there is a video of Darwin practicing his scissor kick on a can. Nicole asks them if they posted it, but they deny it, saying some kids at school did. Nicole tells them the video's title is making fun of them with it saying "Tae-Kwon Dorks," but they deny its negativity, citing the fact that Korean is hard to spell. She then tells the boys about what happened to Richard in the past when he ran around in his superhero costume as the "Cottontail Cavalier," making himself look bad. The boys ask what happened to the cape and Nicole tells them that she took it from Richard and hid it from him. Richard, overhearing Nicole, becomes upset, claiming that she said the president needed it and runs out of the door crying. Nicole reassures the boys that Richard was lucky to have someone who loved him for who he was during that time and it is not wise to act immature and let students laugh at them like Richard did. The boys then tell Nicole that they will give up the costumes and will act more mature than Richard did in his childhood, if it makes her happy.
The boys then sing a piano-accompanied song about how life is about abandoning dreams and expectations and being mediocre. They then say how good they would feel to wear the gis one last time since they are "cured" and can handle it. When they put them on, they find that they are addicted to wearing them and cannot handle it, but they do not care. The next morning they hide their costumes under other clothes and leave for school after being interrogated by Nicole, fibbing that the gis must be in the closet. Nicole then walks to the closet to get rid of the gis and realizes that they have lied to her. She sets off toward the school in the family car. At the school, Gumball takes off his cover and tell the students to watch them break twelve boards at lunch. During lunch, Gumball attempts to break eight boards and fails, injuring himself in the process. He then tells Darwin to lessen the amount to one and fails again, lying on the ground crying while the classmates continue to laugh at his pain and failure. Nicole arrives at that moment and notices Gumball upset with classmates laughing at him and fears that she is too late.
Penny then runs to defend Gumball telling the students that he is brave for being himself. Nicole watches this and then notices that she was wrong to prevent the boys from being themselves. Nearing the end of the episode, she gives Richard back his cape and urges him to put it on. He runs around and then crashes into a wall, the same way that he did in his childhood, reminiscing about how fun that was. Nicole then kisses Richard on the cheek and the episode ends.
This is the first time in the entire series we see Darwin wearing pants. At the part where him and Gumball are dressed for horse riding, Darwin is seen fully clothed. He is also seen wearing pants in the figure skating flashback.
This episode, "The Ex," and "The Ad" are tied for shortest episode title so far, with only five letters.
The video "AWESOME BRICK BREAK" is seen again at the end of "The Secret."
This is the first time Gumball and Darwin are shown older.
In the Korean version of the song, the rising sun scene was cut out.
In the beginning, Gumball and Darwin say please to Nicole in five (technically six) different languages. They are (in order): English (please), French (s'il te plaît), Spanish and Portuguese (por favor), German (bitte), and Hawaiian ('olu 'olu).
In FusionFall, one of Gumball's powers is Tae-Kwon Dork, with the description "Half bear, half shark, half alligator!" which is a reference to this episode.
The music when Richard puts his cape on is similar to the beginning of David Bowie's song "Changes."
During the part where Gumball and Darwin are on the PC, Nicole unplugged the cord to the computer from the outlet, but after the flashback, it is back on, then off, then back on.
In Nicole's first slow motion flashback of Gumball, one can see that there was no karate costume under the coat sleeve Gumball was wearing.
When Richard wears the Cottontail Cape, his belt is brown.
When Gumball and Darwin start to sing "No More Gi," Gumball's ears disappear.
When Darwin states that the children at school call them "The Karate Wieners" in the car, his eyebrows disappear.
In the same scene, his black belt is missing.
Halfway through the episode, when Richard is playing a video game, the dpad on his controller is under his right thumb. That is, the controller is mirror reversed from the normal Super Famicom layout. At the end of the episode, he is playing again, but now the dpad is under his left thumb.
[At the beginning of the episode, Nicole is leaving home via the front door. With Gumball clinging to her leg, and Darwin clinging to Gumball, she drags both of them behind her]
Gumball and Darwin: Please, Mom! Please?
Darwin: S'il vous plaît?
Gumball: ¿Por favor?
[Nicole turns to face her sons as they adopt a kneeling position]
Gumball: We really wanna do karate.
Gumball and Darwin: 'Olu 'olu?
Nicole: [Sighs] Okay.
[The show skips ahead to Nicole driving her car, while Gumball and Darwin are in the backseat wearing karate uniforms]
Gumball and Darwin: Yay!
Nicole: Better not get bored and give it up right away.
Gumball: Mom, when have we ever given something up?
[A series of flashbacks starts; Gumball and Darwin are seen practicing different sports. Every time Gumball and Darwin throw their equipment, a meter fills with 100 dollars and a cash sound effect plays]
Gumball and Darwin: [Throwing their equipment] I hate football! I hate tennis! I hate whipping horses!
[Gumball and Darwin are peacefully skating, when Gumball suddently slams Darwin onto the ice rink]
Gumball: I hate figure skating!
[The meter fills up with 700 more dollars and the flashbacks end]
Gumball: Oh, yeah.
Nicole: Promise me you'll go to the lessons this time.
Gumball: [Scoffs] Pff. Who needs lessons? You already bought us black belts!
[Another 500 dollars pile up on the meter. Then Gumball and Darwin pretend to attack each other, and Nicole sighs]
Darwin: Dude, you look so powerful in your belt.
Gumball: You too, man.
Gumball: Yeah. You're like half shark, half bear, half alligator.
Gumball: Darwin, let's agree to never take these off.
[They shake hands]
[Gumball and Darwin are at home and getting ready for school. They brush their teeth, after which Gumball runs downstairs and tries to jump kick the door]
[He smacks against it and drops to the floor, causing a painting to fall from the wall and onto his face. Next, Gumball pours cereal into a bowl and spins a spoon in his hand]
Gumball: Woo, yah-wah! Haa-yah! [Throws the spoon at Darwin]
Darwin: Yah! [Catches the spoon between his fins] Wahhh. [Eats the cereal]
[Outside, Gumball does a cartwheel, then kicks the bus sign. Darwin follows after him by doing somersaults. The bus pulls up, and the scene skips to the end of the school day. Gumball and Darwin are standing on the sidewalk in front of some of their classmates, and Nicole drives up to collect them]
Darwin: That was the best day of my life! [Performing karate moves] Yah! Yah! Yah!
[Every student, except Penny, laughs]
Masami: Hey, why don't you fight Tina?
[They continue laughing]
Gumball: No, no-no-no. Our karate is strictly for self-defense.
Darwin: To misuse the power in this fin would bring terrible dishonor upon our dojo.
Banana Joe: Haha, do another flip!
[They laugh again]
Gumball: All right, just one more. Ha, for the fans... [Attempts a backflip, but lands face-first]
Banana Joe: Kung-fool!
[Nicole watches from the car, upset]
Nicole: Boys, come on! Time to go.
Gumball: One second, Mom! [Walks up to Penny] Hey, Penny! Hi-yah. [Punches the air, startling her] What do you think of my new style?
Penny: Mmm. Very, um...
Penny: Well... I like to see you happy.
Gumball: Thanks! Wa! [Fakes another punch] You need work on that defense, young lotus. Farewell.
[He gets into the passenger seat, Darwin sits in the back, and they head for home]
[Gumball pretends to hit Nicole, nearly making her lose control of the vehicle]
Nicole: [Chuckles nervously] Everything okay at school, honey?
Gumball: Yeah, school is awesome! Especially when you're wearing one of these.
Nicole: It's just that it... kinda looked like the kids were making fun of you back there.
Gumball: Yeah... Laughing with you can sound like laughing at you.
Darwin: They even called us the karate wieners!
Gumball: I think it's because we always "wien" at karate.
The Inner Warrior
[Back home, Richard is sitting on the couch playing a videogame. Gumball and Darwin are next to him]
Videogame announcer: Suburban Karate Master.
Richard: [After beating some enemies] Ha ha, in your face! Oh, I wish I could kick people like this in real life. [Notices Gumball and Darwin] Hey, nice costumes, guys. [Hushed] You have a spare one?
Gumball: Nah, sorry, Dad. I'm not sure you're ready for the responsibility.
Richard: [Sighs sadly] I understand. [Continues playing]
Gumball: Come on, Darwin. Let's go practice some killer moves!
[They go to the front yard and stand beside a boombox]
Gumball: Okay, dude. You know what a true warrior needs for a good warm-up?
Darwin: Mittens and a scarf?
Gumball: No, Darwin-san. [Turns on the boombox] Inspiration.
[Rock music plays; Gumball and Darwin lip-sync and dance to the song]
Lyrics: Every time I look in the mirror all I see is the inner warrior staring back at me!
You hit hard with your best shot, give it everything you've got. Warrior, be the warrior!
[Nicole and Richard are watching from the window]
Nicole: [Faces Richard] Oh, Richard, I'm so worried about them.
[Richard turns around, revealing that he is also lip-syncing and air-guitaring]
Lyrics: Bring 'em on, let 'em come, they will never keep you down.
Richard: Why? It's a great track.
Nicole: They're obsessed with those outfits, and the kids at school are making fun of them. [Looks at her sons]
Lyrics: Come on, Warrior! Be the Warrior!
Nicole: You know how mean kids can be.
Lyrics: And you're the best that you can be.
Nicole: [Turns away from the window] Richard? [Sees him outside with Gumball and Darwin; Groans, then sighs] I know they're just costumes, but if people make fun of them, they'll never get girlfriends, or a job, and in twenty years' time they'll still be living here and wearing those ridiculous karate outfits!
[Nicole imagines what Gumball and Darwin will be like in the future. She pictures them overweight, unkempt, and playing a videogame in the living room]
Darwin: I think we wasted our lives.
[End of Nicole's imagine spot]
[Later, Gumball and Darwin are using the computer in their bedroom when Nicole walks in]
Gumball and Darwin: Hi, Mom!
Gumball: Check out Darwin's sweet scissor kick. [Plays a video of Darwin kicking a can]
Nicole: When did you post this?
Gumball: We didn't. Some kids at school did.
Nicole: Boys, look at the title. "Tae-Kwon Dorks." I think they might be making fun of you.
Gumball: Nah, they just spelled "Tae-Kwon Do" wrong.
Darwin: Korean spelling is very complicated.
Gumball: There's loads of other fellow senseis on here. Look!
[Gumball plays a video called "Awesome brick break", where a black belt breaks a row of bricks just by using his hand. Nicole suddenly unplugs the computer]
Nicole: [Sighs] I need to tell you a story.
Gumball: Cool! Is it a fable about a great martial arts warrior?
Nicole: Not exactly. When your father was at school, he thought he was the "Cottontail Cavalier."
[Flashback to the time when Richard was still in Elmore Junior High]
Richard: Cottontail Cavalier! [Runs around in his costume, only to crash head-on into his classroom door]
Mister Small, SalLeftThumb, and Patrick: [Laughing] Costumed geek!
Nicole: Leave him alone! At least he's brave enough to be himself.
Nicole: He was lucky there was one girl who loved him for who he really was.
Darwin: What a sad story.
Gumball: But, what ever happened to the cape?
Nicole: Well, I managed to get it off him and hide it.
Richard: [Appears in the doorway; Upset] What?! You mean the president didn't really need my cape?
Nicole: I'm sorry, honey.
Richard: It's because of you I'm mortal! [Runs away crying]
Nicole: You see, that's the kind of state that you can get into when you refuse to grow up.
Darwin: [Dejected] Gumball, I don't wanna be a costumed geek.
Gumball: It's okay, Darwin. Mom, we'll stop wearing the outfits if it'll make you happy.
Nicole: Thank you, boys. I'm so proud of you. You'll see, it's for the best.
[After she leaves, Gumball and Darwin gaze out their window and sing "No More Gi"]
Gumball: Life's about abandoning, dream after dream.
Darwin: Hopes and expectations, float away downstream.
Gumball: It's time to kiss our childish ways goodbye.
Darwin: Grow up? Give mediocrity a try?
Gumball: The games, they have to stop.
[The two remove their headbands]
Darwin: No more hi-yah!
Gumball: Not even a karate chop.
Gumball and Darwin: Face up to what maturity means, and forget about our martial arts dreams.
[They store the outfits in a suitcase and slide it under the bed]
Gumball: Well, I think I'm cured.
Darwin: Me too! I almost think I could put it back on, you know, just one last time, and I would be fine.
Gumball: I reckon if I put mine back on, it would do nothing.
[Gumball and Darwin dress up again and lie on the floor while laughing ecstatically]
Gumball: Oh, it feels so good!
The Karate "Wieners"
[The next day, Gumball and Darwin try to sneak out of the house by wearing their outfits under regular clothing. Nicole hears them open the front door and comes out of the kitchen]
Nicole: Boys? Is that you?
Gumball: Uh... yeah, just rushing off to school, you know? Don't wanna miss any of those, uh, spelling... sums.
Nicole: That's great honey. Now, where did you put those karate costumes?
Gumball: Those old things? I completely forgot about them.
Nicole: But you had them only yesterday.
Gumball: That was yesterday? Well, time sure flies when you're all grown up. [To Darwin] Can you remember where we put them?
Darwin: Beats me.
Gumball: Maybe they're in the closet, bye! [Rushes out, slamming the door]
Nicole: Bye. And now, to get rid of this problem once and for all. [Opens the bedroom closet] What the? They're gone! Wait a minute.
[Nicole rewinds her memory]
[Nicole replays the memory in slow motion]
[She replays it even slower, spotting the sleeve of Gumball's gi under his sweater]
Nicole: Those little fibbers!
[At school, Gumball and Darwin are in the corridor, standing by the lockers]
Gumball: Okay, let's get these dorky clothes off.
Darwin: I don't know, I think I'm gonna keep mine on.
Darwin: Mom's kinda right, this is a bit lame.
Gumball: Are you crazy? [Punches the air, then poses on one leg] Is that lame?
Darwin: Nah, it's pretty awesome.
Gumball: Exactly! Now, our fans are waiting. The Karate Weiners, have returned! [Rips off his extra clothes]
[The nearby students all laugh]
Gumball: People, please, contain your excitement. At lunch break, come and see me attempt... the impossible!
Jamie: What? Are you gonna get a girlfriend?
[They laugh again]
Gumball: No, I'm going to break twelve planks of wood with this hand! [Raises his hand]
Darwin: [Whispering] Are you crazy?
Gumball: No, Darwin, I'M MORE SANE THAN I'VE EVER BEEN!
[Scene cuts to Nicole rapidly driving on the highway]
Nicole: [Angrily] I can't believe they lied to me. I never should've given them those outfits! What was I thinking? [Honks the horn] Out of my way! My kids are in danger! Of becoming their father!
[At the school playground, Gumball is preparing to strike the planks in front of him]
Darwin: Dude, seriously, how're you gonna do this?
Gumball: Ha, easy! I've seen loads of guys do it on the internet. All I have to do is hit it with my hand. Watch! [To the gathered crowd] Karate fans please, can I have a little hush?