The episode begins with Mr. Small giving a boring lecture on the composition of happiness, but he is rather tired (Darwin blames the herbal teas). The day comes to an end, and the students are dismissed. Banana Joe gives Darwin back his pen that he had borrowed. Gumball notices several bite marks on the pen and accuses Joe of biting the pen, who denies this. Unconvinced, Gumball swears to "exact justice" over the trivial act.
At lunchtime, Gumball goes up to Joe and tells him that anything can be solved with a simple apology. Rather than apologizing for chewing the pen, he instead forgives Gumball for his accusations earlier. Gumball is agitated and asks if he can borrow his tube of glue.
Back in the classroom, Gumball is fiercely piercing the tube of glue, to Darwin's confusion. He tells his brother that he is exacting justice, but Darwin still does not quite understand. In an attempt to help him comprehend what he is doing, Gumball smacks Darwin in the face with a ruler twice and asks what the proper response is. Darwin's answer is to pardon the offender, and though a more pleasant alternative, Gumball states it is not justice.
Joe returns to the classroom later that day and finds a note on his desk from Gumball and Darwin that thanks him for the glue. Moved by this gesture, he reciprocates by writing them a card to commemorate their friendship. As he is putting the finishing touches on his card, he finds that his hand is stuck to his tube of glue. Joe is undeterred by this, and continues to keep his spirits high, that is, until he accidentally pulls one of his eyes off.
The school nurse and Mr. Small give Joe medical attention at the nurse's office, unwrapping Joe's bandages afterwards. He does not have his eyes and mouth until Mr. Small puts them on. He advises Joe to be more careful because his tube of glue was badly punctured. Joe claims that the tube was not in such condition when he lent it to Gumball.
Meanwhile, Gumball and Darwin come across the classroom in the state that Joe left it in. Amidst the disorder is Darwin's torn homework. With no other suspect but Banana Joe, Darwin lividly breaks into his locker and begins biting his books and destroy his other possessions. Upon discovering an antique fountain pen, he begins to fiercely chew on it. Mr. Small's voice then speaks over the intercom and calls both of them to his office.
There, he explains to the kids that conflict can be resolved by reminding yourself that an enemy is like you but seen from another perspective, that all people have something in common, and that time is needed to reach an understanding. Darwin says nothing and loses his temper, beckoning Joe into a fight. Mr. Small is scared, and urgently requests that Joe give Darwin the new pen. He presents him the pen whilst regaling a story about his family's most prized possession - a fountain pen used by his great-grandfather Obadiah Banana to sign the registry when he first came to the country.
Joe holds this family heirloom dearly and would be enraged if it were to be violated in any way by anyone. Realizing this, an uneasiness sets on Gumball and Darwin. Mr. Small is touched by the boys' peaceful settlement and thanks them, letting Joe go and filling out a hall pass for Gumball and Darwin. He fumbles on spelling Gumball's name, tears the pass by mistake instead of adding an additional 'L' and decides to print another. The boys' waning patience with him starts to show, and Mr. Small suggests trying his new calming herbal tea. The adverse effects of the tea kick in and Small blanks out with slurred words, allowing the boys to leave without a pass.
Banana Joe is merrily walking down the school halls to his locker, whistling a cheerful tune along the way. In contrast, Gumball and Darwin are sprinting as fast as possible to get there before he does. On their way, they inadvertently set off several accidents: Rocky falling from a ladder, Miss Simian's mug falling on the floor, Alan popping from touching Carmen's spines, and Clayton being slammed by a door. Joe arrives at his locker and finds it open and his belongings vandalized, including the pen.
Gumball and Darwin arrive too late and try to walk away without diverting his attention to themselves. Joe senses their presence and angrily demands that they both turn around and face him. His eyes staring them down, he screams in a fit of rage and races towards them. He trips before hitting either of them, slamming into a water fountain and passing out with a large bruise covering his face.
The boys are both guilt-ridden over ruining his family's most prized possession and causing him additional distress for the rest of the day. In an effort to not appear to have been bullying him, they both decide to beat themselves up and lay on the floor alongside Joe. When he wakes up, Gumball tells him that he beat them both up and they both apologize for ruining the pen. Banana Joe easily accepts their apology. As the three get up on their feet, Gumball feels something weird and searches his pockets. To his surprise, he finds Darwin's pen. The pen Joe borrowed was his and he borrowed Darwin's, and that he chewed his own pen. Instead of hurting Gumball, Joe and Darwin both turn the other cheek and pet him.
Banana Joe and Mr. Small receive slight re-designs, continuing the re-design trend of Season 2.
The tune that Banana Joe whistles is the tune that plays in the title panel of the episode.
On his homework, Darwin gets questions one and three wrong. For question one, his answer was "a lot" when it should have been 51, and for question three, he mislabels a cylinder as a "toilet paper roll."
In Mr. Small's office, the scene where Darwin yells "YO!" marks the first time Darwin was ever drawn with fingers.
Footage from this episode was bizarrely recycled in "The Move."
Banana Joe breaks the fourth wall by making jokes to the viewer.
Banana Joe's whistle theme is a reference to the movie Kill Bill.
Darwin turning his other cheek to allow Gumball to slap him again is a direct reference to the phrase in Christian doctrine that refers to responding to aggressors without violence.
Mister Small: This pie chart is an illustration of the composition of happiness. This portion here represents the ratio of love needed in one's life. This portion here is the- [Gets drowned out]
Gumball: [Chews on his pen] My brain is amazing. When I find something boring it actually prevents me from hearing it. [Mister Small keeps talking, but falls asleep]
Darwin: Hm, I don't think it's your brain, I think it's his. He should seriously give up on this herbal tea.
Mister Small: [Wakes up, inhales sharply] And this portion here represents the- [Bell rings] Class dismissed. [Falls asleep again]
Banana Joe: [walks to Darwin's desk and gives him a pen] Thanks for the pen, dude!
Darwin: No problem.
Gumball: [Picks up pen, it is chewed a little] Hmm... Hey!
Banana Joe: [Turns] What?
Gumball: [Gumball moves his hand to Joe to the pen, he keeps doing this until Joe is swinging his arms] What the derp is that?!
Banana Joe: I don't know, what are you doing?
Gumball: The pen! You chewed his pen.
Banana Joe: [Stops swinging his arm] No, I didn't. [Leaves classroom]
Gumball: What the...can you believe this guy?
Darwin: Relax, dude, it's only a pen.
Gumball: Don't you "dude" me when I'm right! You're supposed to chew things you eat, not people's stuff!
Darwin: What about gum?
Gumball: What about it?
Darwin: You don't eat gum, but you chew that. It's even in the name, "chewing gum".
Gumball: Yeah, sure, but that's specifically made for chewing. It wasn't a chewing pen, you write with a pen!
Darwin: You get a fountain pen, you won't spray water with it.
Gumball: You just don't chew other people's pens! It's the principle! This is what society is built upon, respect!
Gumball: [Walks to Joe in the cafeteria, inhales sharply] You know, Joe, there's nothing that can't be solved with an apology, Joe.
Banana Joe: Hmm... I forgive you for accusing me of chewing the pen.
Gumball: [Inhales sharply] Can I borrow your glue, please?
Banana Joe: Yes, of course. [Gives glue to Gumball] But don't go chewing on it! [Laughs]
[Gumball is puncturing the glue tube with a pencil]
Darwin: What are you doing?
Gumball: [Stops] Exacting justice! [Continues]
Darwin: What kind of justice is there in piercing a tube of glue like a psycho?
Gumball: [Sighs, slaps Darwin with a ruler]
Gumball: Now, what do you feel is an appropriate thing to do in return?
Darwin: Turn the other cheek. [Turns]
Gumball: Which means I can do this. [Slaps Darwin again]
Gumball: That emotion you're feeling, it's your thirst for justice. Quench it! [Darwin bends back ruler, but stops]
Darwin: But what if you offer love instead of hatred? [Strokes Gumball]
Gumball: Oh, yeah, [Strokes Darwin] that is nicer... [Grabs Darwin's fin] but it's not justice! [Slaps himself with Darwin's fin] This is justice! [Slap] This is justice! [Slap] This! [Slap] Is! [Slap] Justice! [Slap]
Banana Joe: [Whistles, goes into the classroom, sees a note on his desk, reads] "Thanks for the glue." [sighs] How swell! I should make them a card to celebrate our friendship!
[Later, Banana Joe is seen making a card. As he pours glitter on it, his hand gets stuck to the tube of glue]
Banana Joe: Gee, that's what I call a sticky situation! [laughs, the container of glitter falls] Whoopsie! [laughs, reaches to it, but gets his hand stuck to a piece of paper] Hmm, Darwin's homework. Well, what am I gonna glue now? [Laughs, pulls homework off, tearing it in half, his hand sticks to the floor] Looks like I'm getting more and more attached to this school. [Laughs pulls it off, gets hand stuck on one of his eyes] Now I'm even bonding with myself! [laughs; grunts and pulls an eye off laughs, looks at eye, screams]
The new Joe
Joan: Okay, Joe, we're going to take the bandages off now, but I just want to warn you that... we did the best we could. [Takes of the bandages and gives a mirror to Joe]
Banana Joe: [Looks in mirror and his mouth and eyes are not there. He drops the mirror and screams with no words. Mister Small puts on Joe's eyes and mouth] Noooooooooooooo-oh! Actually, not bad.
Mister Small: We found this tube of glue stuck to your uh... Anyway, in the future you need to be more careful, this tube was covered in holes.
Banana Joe: But, it wasn't when I lent it to Gumball.
Mister Small: Hmm...
Banana Joe: Hmm... [Gets hand glued to his mouth] Oh, come on!
Gumball: I can understand the glue, but the glitter? That's like putting lipstick on a skeleton, it doesn't make it any nicer. You were right, dude, we should've let that pen stuff slide.
Darwin: [Inhales sharply rapidly]
Gumball: [Darwin tries to break into Joe's locker by banging a book on it] Dude! Please chill out! Here, have some love. [Pats Darwin, who opens the locker and pulls out a book]
Darwin: This, this is for my homework! [chews noisily, pulls out a football] And this is for the glitter! [puts football in mouth and tries to pop it, but fails]
Gumball: Just pop it already! [The football pops, Gumball screams]
Darwin: He destroyed your desk, too, so chew on this![Shoves a jockstrap in Gumball's face]
Gumball: [Pretends to chew on jockstrap] Nyeh, nyeh! That's for my desk that I don't really... care about that much... Nyeh, nyeh! Take that, you banana... [Darwin keeps digging through the locker, Gumball throws the jockstrap behind him]
Darwin: [Grabs a fountain pen] Oh, look! A pen! And it's not chewed! [Chews noisily] What else can we do to it?
Mister Small: [Over intercom] Attention, please, can Gumball and Darwin Watterson please come to Mr. Small's office? Thank you very much.
Resolution and Realization
[Mr. Small chuckles]
Banana Joe: [Chuckles]
Mister Small: [clears throat] Any conflict can be resolved with these three tools. The mirror reminds us that an enemy is just ourselves, but seen from another angle, the water reminds us that we all have something in common, and the hourglass is the time we need to reach an understanding.
Banana Joe: [Screams as Darwin flips an hourglass, filling it, then splashes water on Mr. Small and smashes a mirror right in front of him]
Darwin: Come on, you googly-eyed punk!
Darwin: We got one minute, let's finish this!
Mister Small: Geez, Louise! The pen! Give him the new pen!
Banana Joe: I didn't chew your pen, honestly! But, I bought you a new one, [Pulls out pen] because I myself have a pen of great sentimental value.
Gumball: [Laughs] It's not a fountain pen, is it?
Banana Joe: Actually, yes, it is.
Gumball and Darwin: [whimper, as the pen they were chewing is the one Joe is talking about]
Banana Joe: It's the pen that Obadiah Banana, the founder of our family, used to sign the registry when he first came to this country. [Gumball and Darwin whimper] It was a very expensive pen. I'm not even gonna tell you where he had to hide it to keep it safe! [Laughs] I would lose my mind if anyone chewed on that pen! Anyway, please accept this new pen, and let's be friends again.
Mister Small: Aww! [Snivels]
Gumball: [Whispering to Darwin] Dude, we have to get to his locker before he sees what we've done.
Darwin: Thank you, we gotta' go now, bye!
Mister Small: [Stops them] One minute! Thank you for a beautiful resolution. Banana Joe, you can go, I just need to fill out your hall pass guys. Gum...ball... [Laughs] that's a funny name, isn't it? Ah, do you spell with two or three l's?
Gumball: Two, two l's!
Mister Small: [Laughs] I'm sorry, I just put one. [Rips it up]
Darwin: Dude! You could've just put another one at the end!
Mister Small: Of course! Silly old hippie, I'll do another one; oh, wait, I'm all out, uh I'll have to print one. [Reaches under his desk]
Gumball: Come. On!
Mister Small: Huh?
Darwin: Just print it, please!
Mister Small: Yeah, sure. Here it is, old reliable. [Pulls out a typewriter and blows dust off, Gumball and Darwin cough, Mister Small stares at it] I don't know how it works.
Gumball: Just. Let. Us. Go! Okay?!
Mister Small: You seem a little stressed up guys, you wanna try my herbal infusion? |[Drinks some] It's very good for the nervaallll... [Rails off]
Gumball: Mr. Small? [The tea pours out]
Gumball: Right, come on. [They run out of the room]
Mister Small: Woooohooo!
Joe's family pen
[Banana Joe walks to his locker to admire his pen. Gumball and Darwin are chasing him very quickly, plowing down several classmates and school staff as they go. Despite, Joe gets to his locker first and finds his pen. Gumball and Darwin try to turn around and walk away while Joe is "Mourning" his pen, but he catches them before they get far]
Banana Joe: Hey! Turn around, you cowards.
Gumball: [Laughs] No, thank you!
Banana Joe: Turn around and face the can of butt-whoopin' that I'm gonna open on you!
Darwin: Wouldn't it be better to stay like we are for that?
Banana Joe: [Screams] Turn around!
Gumball: [Inhales] Okay. [He and Darwin turn around]
Banana Joe: [Yells as he charges towards Gumball and Darwin, rushes under them and hits a water fountain, face first. He groans as he slowly becomes unconscious and a bruise covers his face]
Gumball: Augh, that's just great! Now people are gonna come around the corner, see him like that and think we're massive bullies!
Darwin: Which we are! Because of us he lost an eye, and we attacked him with a mirror, we punctured his tube of glue, and ruined everything in his locker, he got a huge brown banana bruise on his little face and we even managed to ruin the most precious thing his family ever owned! [They start crying]
Gumball: [Stops crying] He did chew on the pen, though.
Darwin: [Yells] It doesn't matter! What are we gonna do now? [Gumball starts punching himself in the face, getting a black eye] What are you doing?
Gumball: We need to make it look like he won the fight.
Darwin: [Gasp] And then we'll be even, and we can be friends again, and no one will ever know what horrible people we are! [Starts slapping himself]
Gumball: [happily beating himself up] Banana Joe, please! Not the face!
Darwin: [Also happily beating himself up] Oh, no! Not with the elbow!
[Gumball jumps up and down on his face while Darwin kicks himself. Both become really beaten up]
Gumball: Hey, dude, pull one of my teeth out! [Darwin reaches into Gumball's mouth, but he stops him] Whoa, whoa, whoa, whoa, whoa, that's completely over-the-top, is it? Let's just get into position. [Both fall down next to Joe and act unconscious as Joe wakes up]
Banana Joe: [Coughs] What happened?
Gumball: [Groans] You kicked our butts like a beast, that's what happened.
Banana Joe: Awesome. Oh, hehe, I mean, how did it ever come to this?
Darwin: It's our fault, Joe. We didn't know it was your family pen.
Banana Joe: Well, Obadiah Banana always said that nothing was lost until you lose a friend, and I don't want that to happen to us.
Gumball: [Cries] That's really lame.
Darwin: Group hug? [They try to hug but fail]
Gumball: [standing up] Ow! What is that? [Reaches in his pocket and pulls out a pen] Oh, hey, Darwin, here's your pen. [Holds it out to Darwin]
Darwin: [In an angry and serious tone] What?
Gumball: Your pen, look, its got your initials on it. Wait, [Laughs] oh, man. You know what this means? It means the pen you lent Joe was my pen, not yours, and I was the one who chewed it. I always chew my pen. [Laughs] Isn't that funny? So all this fight for nothing, when I had the pen in my pocket the whole time. Pretty funny, huh, guys? Guys? [Both Joe and Darwin make a fist at Gumball, but start stroking Gumball rather than harming him for starting this tragic episode, Gumball stares in confusion]