The episode starts with Gumball and Darwin reading Anais' diary in their room. The diary explains how Anais made a new friend named Jodie, beginning when Anais gave her a pen. With Gumball imitating Anais' voice, Darwin interrupts him by giving him a warning about reading Anais' diary. However, Gumball ignores him, saying that they did the "pros and cons," which is then shown to be an extensive list, largely of cons, going through much of Elmore. As they read more of Anais' diary, the boys suspect that Jodie is being abusive towards their sister, stealing her lunch, trading science projects so she could get a better grade, and forcing Anais to hold her heavy backpack. Darwin then mentions that Gumball is being overprotective like his mom, but Gumball believes Jodie is a parasite.
In school, Gumball and Darwin try to spy on Jodie. They find a girl that looks exactly like they imagined. Gumball throws Darwin's shoe and knocks her unconscious, but they realize that the duck-girl walking with Anais around the corner is the real Jodie. As Darwin checks to see if the Sparkle Girl is okay, Gumball plans to knock out the real Jodie instead, but Darwin interrupts, saying they should check if Jodie is actually being abusive towards her.
They watch as Anais, supposedly urged by Jodie, puts all of her money in the school vending machine in an attempt to appease her friend, who acts with indifference. Gumball and Darwin react by showing both sadness and anger towards seeing their sister in doing so.
In the next scene in gym, Gumball attempts to throw a ball to hit Jodie. However, Anais protects Jodie, causing her to get injured. Darwin tries to stop him, but he throws another one at Jodie. Gumball explains he is trying to prove that Jodie is "brainwashing" Anais. Darwin tells him to talk to Anais when she is alone. Gumball agrees but throws another ball hastily before leaving, which Anais deflects again.
In the halls, the three siblings have a conversation about Jodie. Anais gets mad about Gumball reading her diary, using her voice without permission, and trying to hurt Jodie, but is touched that they cared that much about her. Gumball tries to tell her that Jodie is a parasite, but Anais ignores him and insists that Gumball leaves her alone and not ruin her friendship.
At lunch, right as Anais chimes in to pay for Jodie's lunch, Gumball jumps in, offering them a bagged lunch prepared by Richard instead. Anais, suspicious about the one that he gave Jodie, asks Gumball if they are all the same, which Gumball affirms. Still doubtful, Anais gives the bag he gave Jodie to Gumball instead. The two end up shuffling the bags around for a while before Rocky jumps in and rapidly shuffles them up, trying to make it fair for everyone. They all proceed to nervously take a bite of their sandwiches, though all of them end up unharmed. The scene then cuts to Richard, who ended up getting the poisoned lunch, suffocating while trying to call the hospital.
Gumball and Darwin ultimately decide to call Jodie. Using Anais' voice, Gumball tells Jodie that they should stop hanging out, causing Jodie to cry. The two immediately feel bad for their actions and try to approach Jodie to apologize. When they get closer, however, they find Anais and Jodie fused together. Gumball reacts in shock, telling Jodie to leave his sister be, but the creature runs off, trying to escape. Eventually, Gumball and Darwin manage to trap Anais and Jodie in a box that, per accident, is sent flying into the infirmary.
In the infirmary, it is revealed that Anais is the parasite. In the end, Anais unlatches Jodie and has remorse on how she acted towards her, asking Jodie gives her a second chance. By that point, however, Jodie had fled the room, causing Anais to chase after her, ending the episode.
[Anais' diary opens up. As Gumball, in Anais' voice, reads, a scene plays out, showing a depiction of Anais handing "Jodie" a pen. "Jodie" smiles at Anais]
Gumball: [Anais' voice] Dear diary, today it happened, the thing I wanted most, I made a friend. Her name is Jodie. She needed a pen, so I lent her mine. Which is why I wrote this entry with a paintbrush dipped in yogurt. But she smiled at me! From this moment on, I knew we were going to be best friends.
Darwin: Dude, that's a really good impression.
Gumball: [Anais' voice] Thank you.
Darwin: But I'm still not convinced we should be reading this.
Gumball: Ah, come on, we did the pros and cons.
[Gumball and Darwin look at their list of pros and cons. The list shows only two pros and an indeterminately large amount of cons going off the sheet of paper, out of their house, through town, and on top of Alison]
Gumball: Okay, quite a few cons. But on the pro's side... [Anais' voice] I hope I get my growth sprout soon, I'm tired of using the cat door at Granny Jojo's house because I can't reach her doorknob.
Darwin: [Chuckles] Okay, let's just read a little more.
Gumball: [Anais' voice] Today, I got to sit with Jodie in the cafeteria.
["Jodie" is shown slapping a sandwich out of Anais' hands and stealing her lunch tray]
Gumball: [Anais' voice] She still looked hungry after finishing her lunch, so I gave her mine. Jodie was scared she'd get a bad grade on her science project, so I gave her that too.
["Jodie" is shown taking Anais' project and giving Anais her's, a potato and a lightbulb]
Gumball: [Anais' voice; Chuckles]: She was right! Science is not her strength. But I was happy to help my friend.
[Anais tries to demonstrate "Jodie's" project, but it causes an explosion. Anais is then seen laying in the infirmary. "Jodie" walks past her, having gotten an A+ using Anais' project. Anais waves at her, but "Jodie" doesn't notice]
Gumball: [Anais' voice] Later on, we walked back home together. She said she was tired, so I carried her bag.
["Jodie" is shown briskly walking before the camera pans over to reveal Anais following behind carrying a heavy backpack]
Gumball: [Normal voice] Wait a minute, this Jodie is taking credit for Anais' work, getting her to carry her stuff, and eating her lunch! You know what she sounds like?
Gumball: No! I meant -- [Sighs] You know Anais. In spite of being clever and sarcastic, she's also fragile and weird, and she has trouble fitting in, and this person is taking advantage of her weakness! And you know what that's called?
Darwin: A Gumball?
Gumball: Uh, yeah, but -- [Snaps] I'm the only one who should be allowed to do that, okay?! [Calmly] I just don't think Anais should hang around with that kind of person.
Darwin: Now you sound like Mrs. Mom.
Gumball: [Nicole's voice] No I don't! [Normal voice] I refuse to let our little sister get tricked by this parasite!
[In the school hallway, Tobias and Leslie are having a conversation. Gumball and Darwin peer from around the corner of the hallway]
Gumball: Can you see her?
Gumball: Look harder!
[Darwin puts a toothpick in his mouth and makes a tough-looking face]
Gumball: No, I meant -- [Gasp] There she is!
[Gumball and Darwin spot who they imagined Jodie to look like opening her locker]
Darwin: Huh, funny. She looks exactly how I imagined.
Gumball: Darwin, give me your shoe. [Darwin gives his shoe to Gumball] This will teach you for toying with my sister's feelings!
[Gumball hurls the shoe at the girl, causing her to shriek and faint. Anais then walks into frame accompanied by the real Jodie]
Anais: So Jodie, are you hungry? Friend?
[Both Gumball and Darwin gasp]
Gumball: [To Darwin] Do something!
[Darwin runs to the knocked-out girl, takes his shoe, and runs back]
Gumball: No! about her!
[Darwin runs back to the girl and checks her pulse. He sighs, relieved, and runs back to Gumball]
Gumball: I got an idea.
Gumball: Give me your shoe.
Darwin: Um, how about we just wait and see if she's actually as bad as you think?
Gumball: [Sighs] Alright.
Anais: Jodie, we're friends right?
Anais: Best friends?
Jodie: Well, uh...
Anais: Um, do you want some candy? [Puts a few coins in the vending machine]
Jodie: Um, okay.
Anais: Whatchu' want? Don't worry. I'll buy one of each. That's what friends are for. [Puts several coins in the vending machine, then presses the buttons] Yeah.
[Anais chuckles. All the candy falls out of the vending machine. Anais grabs a handful and tries to give it to Jodie, who steps back with a concerned look]
Gumball: I don't know what to feel, sadness for our little sister, or angry at that horrible freeloader!
Darwin: How about both?
[Gumball and Darwin cry with one side of their faces and make angry looks with the other]
[In the gym, Anais, Jodie, and Clare are throwing a ball around. Gumball, hiding behind some gym equipment with Darwin, then throws a dodge ball towards Jodie. Anais sees it, gasps, and takes the hit, giving her a black eye]
Anais: [Gives a thumbs up] I'm okay, Jodie.
[The scene cuts back to Gumball and Darwin]
Darwin: What exactly are you trying to do here?
Gumball: [Angrily] Prove that Anais has been brainwashed by Jodie! Look, I'll throw another one. [Picks up another dodge ball]
Darwin: No, no, no! I-I believe you. How about you stop throwing things at innocent girls and we speak to Anais when she's alone?
[Gumball groans and the two walk away]
Anais: [Out of frame] Hey, Jodie. You want me to carry your bag?
[Gumball runs back into frame and tries to hurl another dodge ball at Jodie. It hits Anais instead]
[The school bell rings. Gumball and Darwin confront Anais in the hallway]
Darwin: Hey Anais, we need to talk.
Anais: What about?
Gumball: [Anais' voice] Dear diary, today I made a wretched friend who takes advantages of me and deserves to have objects thrown at her face. [Anais kicks Gumball's leg] Ah! Ahhh, what was that for?
Anais: That was for reading my diary. [Kicks Gumball's other leg] And that was for using my voice without permission. [Slams locker door into Gumball's face] And that's for trying to throw things at my friend. [Kisses Gumball] And that's for worrying about me.
Gumball: You don't understand! She's not your friend, she's a parasite! First, she uses you to get stuff. [Demonstrates by hugging Darwin] Then, when you think you guys are friends, [Gumball climbs on top of Darwin and merges into a hideous alien-like creature] she takes over your mind, attaches herself to your body, and before you know it, she turns you into a fungus thingy so that she can release her spores, contaminating more people and destroying civilization as we know it! ..I stole that last line from a zombie video game. It's just, I don't want you to feel sad when you realize she's not a true friend.
Anais: Look, for once I get to hang out with someone who gives me my own problems, rather than someone who makes me fix theirs.
Gumball: Who's that? sounds awful.
Anais: You! [Walks away] Please don't ruin this for me!
Gumball: Follow her!
[Tobias walks past the Gumball and Darwin creature. It notices Tobias and attacks him]
[Jodie queues for her food while Anais stares at her awkwardly in front]
Rocky: That will be five bucks.
Anais: I'll pay for me and my friend.
Gumball: [Gumball interrupts] No no no no, that chicken is so old it came before the egg. Come on, lunch is on me!
[At the table]
Gumball: [Gumball puts the bags of sandwiches on the table and gives a specific one to Jodie] Here! Help yourself Jodie, I know how much you like free stuff.
Anais: Hmm.. Who made these?
Gumball: Oh, just me and dad.
Anais: So they're all the same. Right?
Gumball: Of course. [Looks at each other]
Anais: Great! Then let's eat! [Switches the sandwich bags]
Gumball: Oh wait! You don't want that one, Jodie. I think dad was running out of mayo by the time he made it. Here! Have mine, it's got loads of mayo in it.
Darwin: Oh you won't want that then! It'll be soggy. Here, lets swap. I love mayo.
Gumball: Whaaat? Noo! [Talking through his teeth] You hate mayo, remember?
Darwin: What? Oh! Yes! Uh, I just remembered. I hate mayo. [He switches the sandwich bags and Anais does it, too. Gumball, Darwin, and Anais continue to switch bags, much to Rocky's dissapointment]
Rocky: Oh, for derp's sake! [He switches the bags the right place] There! Now it's fair for everyone.
[Gumball, Darwin, Anais, and Jodie nervously raise the sandwiches to their mouths and reluctantly take bites]
Gumball and Darwin: Mmm.
[Anais and Jodie nod along. The scene cuts to Richard back home, who is suffocating on the floor. The phone hangs just above his hand]
Larry: [Voice] Hello, 911. Hello?
[Back in the cafeteria]
Anais: What do you think you're doing?
Gumball: The only sensible thing: poison the sandwich so your so-called friend gets the message that -- okay, now that I said it out loud, I realize it sounds kinda wrong.
Jodie: We think it's time for you to go.
Gumball: Okay, wait, I'm confused. Are you using the "royal we" now? Are you gonna start playing doubles tennis on your own. When you go to the bathroom, are you gonna say, [British accent] "We're having two weebies!" LISTEN TO YOURSELF! You're not even making your own decisions anymore!
Jodie: That's ridiculous. Of course we're --
Anais: -- making our own decisions. We are still --
Jodie: -- separate people.
[Gumball and Darwin gasp]
Gumball: Did you see that?! She's taking control of your mind! She's not just a social parasite; she's an actual parasite!
Anais: You are being—
[Jodie leaps on top of Anais in a similar manner to how Gumball and Darwin previously demonstrated]
Gumball: L-look at it! Just like a leech!
Jodie: Jodie is just—
Anais: —tired from playing dodge ball.
Gumball: But... Are you kidding me?! She can walk on her own two feet like everyone else in this school! [Alan floats by] Apart from him. [William flies by] And him. [Carrie floats by] Okay, and her, but you get the idea!
[Jodie and Anais walk off]
Darwin: What are we gonna do?
Gumball: [Anais' voice] I think I have an idea.
[Darwin peeks across the hallway to Jodie, who is hiding behind a corner]
Gumball: Is she alone?
[Gumball dials a phone; Jodie's phone rings]
Gumball: [Anais' voice, through the phone] Hey, Jodie. I think we should stop hanging out. I would say it's not you, it's me, but I would be lying. It's definitely you. You're a scrounging, bloodsucking parasite. Also, you smell like medicine, which is weird, so I thought I should mention it. Good-bye. Actually, you know what? Bad-bye! Oh, also if you see me, can you tell my brother where I am? 'Cause he's looking for me. [Hangs up] So?
Darwin: I think you went too far.
[Gumball and Darwin check on her. She cries]
Gumball: Hey, Jodie, please don't cry. I-It wasn't really Anais on the phone; I just thought you were being a bad friend to her.
[Jodie makes distorted grunting]
Darwin: Uh, Jodie, do you need a tissue?
Gumball: On a bucket?
[Jodie screams. She is shown with Anais fused together; Gumball and Darwin scream]
Gumball: Hey, get off my sister's everything!
Jodie and Anais fused: Leave us alone!
Darwin: They're getting away!
[The fusion of Anais and Jodie bumps against the lockers while they are running through the hallway]
[Scene cuts to the library. Gumball and Darwin enter through the door]
Gumball: Hey! Let go of my sister, you parasite!
Jodie and Anais: I'm not a parasite!
Gumball: Let's throw some scientific facts at 'em!
Darwin: Good idea!
[Gumball and Darwin get books from bookshelves; Darwin reads from a book]
Darwin: "A wolverine can kill a moose! The colour of the universe is a shade of beige called Cosmic Latte! Male sea horses can—"
Gumball: I meant that we should throw books! I said throw some facts 'cause it was, like, a-an action movie quip. [Sighs] Never mind. Just throw books.
Darwin: But we'll hit Anais.
Gumball: Just avoid the pink parts.
[Gumball and Darwin throw books at Jodie and Anais]
Jodie and Anais: Ow! Ow!
Gumball: This is worse than I thought. They're even feeling the same things!
[Jodie and Anais run between Gumball and Darwin; they hiss and grunt]
Gumball: There's only one solution left.
Darwin: It better not be throwing a shoe at them!
Gumball: Why? You got something better?
Darwin: We take them to the infirmary!
Gumball: Okay, that is actually better. I'll set up a trap, you lure them in—
Darwin: A humane trap, please.
Gumball: [Scoffs] Of course.
[Jodie and Anais run through the hallway. Darwin blocks them, and they go the opposite direction. Darwin blocks them again, leading them right into Gumball's trap. As Gumball pulls a rope, they trip over, slide in a puddle of oil, land roughly into a box, and the box falls down the stairs, making a hole through the infirmary door. Clashing and clattering is involved]
Darwin: Is that your idea of humane?!
Gumball: I thought she would see the yellow rope, duck, slide in the oil, and get delicately trapped inside the box. I-I didn't think it would, well, you know—
[The infirmary catches on fire, leading the nurse to utilize the fire extinguisher]
Gumball: That'll be the candle I put in the box in case they were scared of the dark.
[Darwin stares furiously]
Gumball: At least they're in the infirmary.
In the Infirmary
[Gumball chuckles nervously. Scene cuts to a surgery-like scene, with Jodie and Anais on the bed]
Gumball: Nurse, we need a C.T. scan, an MRI, and an X-Ray— stat!
[Scene reveals to be in normal atmosphere]
Joan: Right, and I want a six-figure salary, a cabriolet, and a pension plan. Unfortunately, this the school infirmary, not NASA. All I have here is Vitamin C, some teddy-bear-shaped Band-Aids, and a couple of lollipops. What's the problem, anyway?
Gumball: Our sister got infected by a social parasite!
[The creature groans; Ms. Markham examines them. She checks the fusion's heartbeat, which seems to be quick, but is actually shown as Gumball thumping the table with his fingers in worry]
Gumball: Uh, oh, sorry. [Clears throat] So, what do we do?
Joan: Pretty simple— your sister needs to let go of that poor girl. She is the parasite.
Gumball and Darwin: What?!
Jodie: All I wanted was to borrow a pen.
[Scene cuts to a flashback of the actuality of the diary. Anais hands Jodie a pen; Jodie smiles]
Anais: [Raspily] Frie-e-e-e-end.
[Scene cuts to Jodie eating lunch. Anais enters, feeding her food from her own lunch]
[Scene cuts to Anais, offering Jodie her science project forcefully]
Jodie: I-I-I-I can't accept this.
Jodie: Uh, uh, okay, okay.
[Scene cuts back to present reality]
Anais: I'm sorry. I was really excited and got carried away. I'll let go of you now.
[Anais separates from Jodie offscreen. Apparently, it is a horrific scene; all those present are repulsed and there is ooze all over both of them]
Anais: I hope you can forgive me. I-I know I acted crazy, but it's because I never had a school friend before. So I got a little clingy. I think if— if you gave me a second chance and got to know the less insane, more normal me, we could actually be real friends. What do you say?
[It is shown that Jodie has escaped from the infirmary]