When Gumball and Darwin realize Grandpa Louie has no friends, they create one called Muriel, when Granny Jojo finds out Louie has been spending time online with another woman, Muriel not existing is not going to stop her from being destroyed. 
The episode starts with Gumball on his computer. Darwin asks if Gumball searched his name online again, but Gumball trembles at the thought of those "weird drawings" of him. Instead, he is searching other people's names on Elmore Plus. When Gumball shows Louie's profile to Darwin, he feels pity in seeing Louie's status updates and lack of online friends. They decide to help by creating a fake profile online to communicate with him under the guise of "Muriel."
Once Louie accepts the friend request, he proceeds to ramble incessantly about his life. However, Gumball grows tired of it quickly, with each vibration of his phone interfering with his day and preventing him from sleeping at night. Ultimately, the message seems to indicate that, while his relationship with Granny Jojo started out joyously, he now feels trapped in her presence.
Eventually, Gumball and Darwin decide that they have had enough and want to tell Louie the truth by "meeting up." However, things take a turn when Louie agrees, saying that he believes them to be "more than just Elmore Plus friends."
Meanwhile, at Joyful Burger, Louie tries to hide Muriel from Granny Jojo, who gets suspicious of him. Ultimately, Louie accidentally slips out his relationship with Muriel, causing Granny Jojo to get on the offensive and, seeing that the two plan to meet at the Elmore Mall, sets out to take her down.
Back at home, Gumball and Darwin receive word that Granny Jojo is after Muriel, but the two initially dismiss the warning as they made the character up. However, after searching up where the profile picture came from, they find that she works at the mall; thus, they have to protect the "Fake Muriel" even though she has no knowledge of the scheme.
At the mall, the pair try to protect Fake Muriel (while being repeatedly bombarded by a real Muriel). Eventually, at the pet store, they are forced to tell the truth to calm Granny Jojo down. Louie is disappointed and angry at the prospect of being literally catfished. Darwin objects that none of it would have transpired had Granny Jojo not been so controlling of Louie. He, in turn, explains that by saying, "more than just Elmore Plus friends," he simply meant he wanted a friend in real life, something that Granny Jojo never let him have. Realizing her mistakes, she decides that she will let him have just one friend.
Gumball and Darwin get on the computer to see who Louie's new online friend is, only to find that it was Granny Jojo. They sigh, ending the episode.
This episode reveals that Betty and Donald are married.
Louie mentions having had a teacher named "Mr. Klein" in his youth, likely a reference to former storyboard supervisor Chuck Klein.
Rocky'sElmore Plus profile contains references to "The Slide." On the same page is a picture of Rocky in a suit, similar to "The Boss" (though the suit he was wearing in the picture was real, while the suit from "The Boss" was made of spray).
In the close-up of Granny Jojo's angry face, music from "The Joy" is reused.
On the walls of the pet store is the motivational poster of a groundhog lifting a weight that Gumball showed to Richard in "The Poltergeist." The photograph displayed below it is a modified version of one of the cat pictures featured in "The Internet."
The snake that tries to strangle Darwin in the pet store is the same one Penny encountered in "The Romantic."
The title of the episode may be a reference to the MTV TV Show "Catfish".
The show is presumed to have created the term Catfish, as referring to someone who pretends to be someone they are not via the internet.
The pictures of Gumball that momentarily show when Gumball is remembering things he has seen from looking up his name is a direct reference to fan-art that can be seen throughout multiple social media sites, including DeviantArt.
The line "four score and seven years ago" is a reference to the text of "Gettysburg Address" used in Lincoln's speech, referring to when the Declaration of Independence was signed.
The scene where Granny Jojo is covered in flowers is a reference to American Beauty.
When Louie describes his current view on Granny Jojo, Mussorgsky's Night on Bald Mountain is heard in the background.
The painting that Gumball mistakenly creates while trying to paint Banana Joe is a reference to the American artist Jackson Pollock.
When Louie is sending messages via mobile, it relates to many teenagers sending small portions of a sentence in chats.
Granny Jojo destroys a self-serve checkout machine with attacks resembling those of E. Honda from Street Fighter. Namely, his hundred hand slap, and sumo headbutt.
Rocky's demonic profile picture from "The Slide" appears on his Elmore Plus page in certain angles.
When Louie says "Tell me more about you" on Elmore Plus chat, Gumball is using his own account when he should be using the fake Muriel account. Otherwise Louie should have known it was Gumball.
Louie's story started four scores and seven years ago. A score is equivalent to 20 years, thus his story started 87 years ago, but he stated in "The Signature" that he was 72 years old.
His message reads, "...four scores and seven years ago..." but Gumball reads "...four score and seven years ago..."
When Louie warns Muriel about Granny Jojo coming after her, he refers to her as his wife. But when Granny Jojo attacks a self-checkout register during a flashback, she refers to Louie as her boyfriend.
It could be noted though, that during that time, Louie and Granny Jojo were not married.
In the same message, he refers to Granny Jojo as a rodent, despite her being a rabbit, which are lagomorphs.
[The episode begins with Gumball and Darwin at home in their bedroom. Gumball is busy browsing the internet on his computer]
Darwin: Are you searching your name online again?
Gumball: No, I've learned my lesson. Every time I close my eyes, I can still see those weird drawings of me.
[Gumball shudders and cries out in fear as he recalls different fanart]
Gumball: [Traumatized] Who draws that stuff? No, I'm searching other people's names. Like, did you know that Rocky trained at a mime school for a whole year?
Darwin: Hmm. [Mimes cleaning a window] I can see how those skills would be useful to a janitor.
Gumball: And did you know that Mr. Small released an album?
[The screen shows an image of Mr. Small, with a tube inserted in his mouth]
Darwin: What does it sound like?
[Gumball clicks play, and a throaty, buzzing sound resonates]
Darwin: [Disturbed] Uh, like the cover would suggest.
Gumball: And you want to know what's even weirder? Grandpa Louie has an Elmore Plus profile. [Reads] "Just a fun guy looking to get into your friend zone."
[Both of their faces fully recede into their bodies]
Gumball: I just cringed all the way back into my lower intestine.
[The computer beeps, and they return to normal]
Darwin: Oh! He sent us a friend request.
Gumball: Being friends online with your grandpa is like taking your mom to the prom.
Darwin: But he's got zero friends. And look at that post. "Anyone up for a game of squash?" No one replied. He probably ended up playing against the wall.
Gumball: Squash, the lonely man's tennis.
Darwin: [Depressed] Or here, he typed "How to make friends online." He then realized it wasn't a search bar, so he typed "Sorry, I don't know who wrote that." Then he typed, "What is the term for someone updating your status as a joke?" Then he must've banged his head on the keyboard, because it says-- [Speaks gibberish; Tears up] This is so sad!
Gumball: [Bluffing] No, it's not.
Darwin: Dude, stop hiding your tears. I know you feel sorry for him too.
Gumball: No, I don't.
Darwin: Don't repress your feelings.
Gumball: I feel nothing for him. [Whispers] Nothing.
Darwin: I know you're holding back, because--
[Water jets gush from Gumball's eyes, knocking Darwin to the floor as he screams]
Darwin: [Stands up] Okay, are you--
[The same thing happens again, and Darwin gets back up]
Darwin: So, you agree we need to help Grandpa Louie.
Gumball: [Gasps] You know what we should do? Pretend to be his friend online by creating an entirely fictitious persona.
Darwin: Now, when you say "should," surely you mean "definitely shouldn't."
Gumball: [Taps the keyboard] Nope. I mean "have."
Painting a Muriel
[Gumball and Darwin get off the bus at school and stand on the sidewalk]
Darwin: Isn't Grandpa Louie too old to have imaginary friends?
Gumball: She won't be imaginary to him. And besides, that comment was ageist. You're never too old to have imaginary friends. [Privately] I still love you, Mr. Smiggles.
[He exchanges an awkward glance with Darwin, then heads for the entrance. A sudden gust of wind rustles the papers Darwin is holding]
Raspy Voice: I love you, too.
[Later, the brothers are talking in the school's playground]
Gumball: Ah, don't worry. It's just a little white lie.
Darwin: But why do you have to make her a woman?
Gumball: [Acts feminine] It's just how I feel inside.
Darwin: [Sighs] Okay, so what's her name?
Gumball: [Breathes deeply] Muriel.
[His cellphone beeps, and he pulls it from his pocket]
Gumball: [Gasps] Grandpa Louie's accepted! And he wants to know more about Muriel. Uh... what are old people into?
Darwin: [Shrugs; Mumbling] I dunno.
Gumball: Um. [Types] "I like mortgages, and v-voting. And... I drive cars with my driver's license."
Darwin: Oh, and putting cucumbers on your eyes.
Gumball: Yeah. [Types] "Please tell me more about you."
Darwin: [Nods in agreement] Hm.
Gumball: [Reads the texts] "Thanks for asking. My story begins four score and seven years ago, back when things were very different."
[Gumball's voice fades, replaced by Grandpa Louie's]
Louie: ...things were very different. As a young boy, I had no trouble making friends. In fact, I was so popular, I got invited to all the birthday parties. And when they got older, their weddings. Even their honeymoons... which was a bit awkward. I was so well-liked, they used to call me "Fluey Louie," after the Spanish Influenza which was very popular at the time.
[During the non-stop texts, Gumball's phone continuously vibrates. It interferes with his daily activities, such as schoolwork, eating lunch, and painting]
Louie: Even animals loved me, apart from horses. But I never trusted horses. Their faces are too long, and they have mohawks. I was so popular at school, I even became friends with the teachers. We had such crazy nicknames for each other, like "Mr. Klein," or "Sir," or sometimes accidentally, "Dad." When I got older, things got even better. I met Jojo. She opened my eyes to something greater. Love. Everything about her was magical. Her luscious lips, her flowing hair, her cutie patootie.
[Gumball is standing at a bus stop with Darwin, when his cellphone comes to life]
Phone: I'm sorry, but I refuse to picture that last image. Goodbye, cruel world. [Throws itself to the cement]
[Louie's messages carry on through the night, the flashing of the computer monitor keeping Gumball and Darwin awake]
Louie: Our romance was ravenous, insatiable, our hearts melting with hunger until we consumed each other like a pair of feasting lions. We spent every hour of every day...
[Gumball gets out of bed and leaves the room, with Darwin following after him]
Gumball: I'm gonna go bathe in disinfectant.
Darwin: Good idea. I'm gonna steam-clean my brain.
Louie: But very soon, her loving arms refused to let go of me, and she kept me captive. Her tender fingers now the bars of a gilded cage, from which I can never escape! Anyhoo, enough about me. What's your favorite food?
[In the living room, Gumball is on the sofa, using the laptop. Darwin is seated beside him, observing]
Gumball: [Types] "Edible. Listen, I gotta go."
Darwin: [Reads] "That's fine. Just take your phone so we can keep messaging."
Gumball: [Replies; Reads responses] "I'm going places where I can't use my phone." "Where?" "The cinema." "Just use silent mode?" "The bathroom." "Camera off mode?" [Annoyed] "What if I'm in the middle of a hold-up or something?" "Hand's free mode?!" Aah! He just doesn't give up!
Darwin: What are we gonna do?
Gumball: I don't know. You're the one who wanted to help him.
Darwin: What?! You're the one who came up with Muriel!
Gumball: [Sighs] You're right. [Loudly] I blame Muriel!
Darwin: [Grabs the laptop] I mean I blame you! We have to tell him the truth and put an end to this before he starts telling us things we're too young to know about. [Types] "We have to meet. There's something you should know."
Gumball: [Reads] "There's something you should know, too. I thought I needed a friend, but the way you patiently listened to me made me realize something else. Muriel, I think we're more than just Elmore Plus friends?!"
[Meanwhile, Louie is in a booth at the Joyful Burger restaurant. He quickly conceals his phone when Jojo approaches him]
Louie: [Nervous] Oh, hello pumpkin. Uh, didn't see you there.
Granny Jojo: [Suspicious] You look guilty.
Louie: What? [Chuckles] That's weird, because my conscience is so clean. Spotless.
Granny Jojo: You're lying. Your eyes always look to the right when you're lying.
Louie: No, I'm not.
[His eyeballs rotate in their sockets, after which his fur lights up]
Granny Jojo: What's that? [Rips the cellphone out, leaving a bald spot] Sorry, honey. Was that your favorite shirt?
Louie: [Groaning] No, it was my favorite skin.
Granny Jojo: [Shows him the screen] What's this heart icon?!
Louie: What? Oh, that. That's just a health application telling me how unhealthy I am.
[Jojo glares at him, causing Louie to tense up and sweat. She starts to laugh, and he joins in]
Granny Jojo: [Returns the phone] I thought I'd found you cheating on me.
Louie: I know, me too. For a second there, I thought you were looking at all my messages to Muriel.
Granny Jojo: Muriel?! [Enraged; Swipes the phone back] Who's Muriel?! [Reads] "I want to be more than just Elmore Plus friends?!" "Let's meet in real life?!" "Two PM at the mall?!"
Louie: Wait, I can explain!
[Jojo snarls at him. Back in the Wattersons' living room, Gumball and Darwin are fighting over the laptop]
Gumball: Are you crazy?! Why do you want to meet with him?
Darwin: Because we have to come clean.
[A message pops up on the monitor]
Gumball: "Muriel, if you happen to see a two hundred pound raging rodent in a dress running towards you while screaming and wielding a sledgehammer, please stay out of her way. I know that's good advice generally, but in this specific instance, it's most likely my wife coming after you."
Darwin: Wait, it's fine. Muriel doesn't exist. You made her up. Where'd you get her profile picture form?
Gumball: Meh, just randomly online. [Taps the keyboard] Okay, there's one funny piece of news, and another not so funny piece of news.
Darwin: Funny one first, please.
Gumball: When I search for her photo, all the related pictures are of guinea fowl.
[The brothers share a laugh]
Gumball: And the not so funny news is, that the picture comes from the mall's website. She works there.
[On the road, Jojo is recklessly driving through traffic as she rushes to Elmore Mall]
Louie: Jojo, please! I never meant to hurt you!
Granny Jojo: Of course you didn't. Now would you mind closing your window, dear?
Louie: Sure, why?
[The car swerves and crashes through a barricade, causing Louie to smack his head against the glass]
Granny Jojo: So you can feel on the outside how I feel on the inside!
Louie: So now we're even?
Granny Jojo: Yes, we are. [Furious] But I'm not even with Muriel!
[Gumball and Darwin enter the mall's parking lot. On their right, they see the woman whose likeness they borrowed, while to their left, Granny Jojo is racing toward her]
Gumball: [Shouting] MURIEL!
[An entirely different person answers his call]
Muriel: Yes, dear?
Gumball: Oh, right. [Speaking quickly] Uh, so basically we made a fake profile online to be friends with our grandpa because we felt sorry for him. And then her made-up name is Muriel, but I forgot that wasn't her real name, which is funny because when I called her, you answered. Now you should probably jump out of the way, because our grandma is about to run you over with her car.
Gumball: Hm. Maybe I shoulda just said-- [Shoves her away] WATCH OUT!
[Jojo spots her target on the other side of the lot, and accelerates]
Granny Jojo: There she is!
Gumball: [Steps in front of the car] Grandma, stop!
[She slams the brakes and veers to avoid hitting Gumball. The vehicle flips over his head and rolls to a stop by the entrance. Punching the door off of the car, Jojo continues her pursuit inside the mall]
Granny Jojo: Where is she? [Sees fake Muriel boarding the down escalator; Growls]
[Gumball and Darwin go after their grandmother, but she is already on the second floor, trying to take Hexagon Lady's shopping cart]
Gumball: We need to stop Granny Jojo!
Hexagon Lady: They're my groceries! Give it back!
[Jojo knocks Hexagon Lady over, then pushes the cart onto the same escalator]
Muriel: [Comes on-screen] Yes?
Gumball: [Groans] Not you!
[He sprints to the escalator, and, with a leaping dive, hits the button to reverse its direction. The runaway cart stops at the bottom, and fake Muriel walks away unscathed. Jojo follows her from above, stopping by the railing]
Granny Jojo: There she is!
[Climbing onto the rail, Jojo prepares to use a banner decoration as a rope swing, but Darwin unties the other end and she falls backward instead]
Granny Jojo: Ohh! My hip replacement.
[Jojo catches up with fake Muriel as she is leaving a grocery store]
Granny Jojo: [Roars; Resumes chasing her] You're not getting away from me!
[She picks up a baseball bat from a nearby display and prepares to throw it, but Darwin quickly swaps it for a boomerang]
Granny Jojo: Stop meddling! This is none of your business!
Darwin: Granny Jojo, there's been a mistake! Muriel-- [Gets knocked out by the boomerang]
Granny Jojo: [Holds him gently] Oh, honey, are you okay? [Notices fake Muriel; Drops Darwin] Eh, a rest will do you good.
[At the pet shop, she meets up with her unwitting prey once more. Reaching into a cage, she pulls out a striped snake, as Gumball and Darwin race up behind her]
Gumball: G-Granny Jojo, you don't get it!
Granny Jojo: I may not, but she certainly will!
[Jojo tries to toss the snake, but a dove flies from her hand instead. The bird delivers an olive branch to fake Muriel]
Fake Muriel: [Pleased] Ahh.
[Granny Jojo turns to face her grandchildren, while Gumball attempts to remove the snake now wrapped around his screaming brother's head]
Granny Jojo: That's the exact opposite of the message I was trying to send!
Gumball: You don't understand! Muriel doesn't exist! We made her up!
Granny Jojo: Eh?
Louie: ...problem then.
Granny Jojo: Well then, who's that?
Gumball: We just used her photo. [Puts the snake in its cage] We made her up so Grandpa Louie could have a friend online.
Louie: [Upset] What?! Do you know what a cat and a fish pretending to be someone else online is called?
Gumball: Cat... fishing?
Louie: No! It's called... wait. Actually, yes, that is what it's called.
Gumball: But if we lied to make you happier, is that really so wrong?
Louie: It is literally illegal.
Darwin: None of this woulda happened if Granny Jojo wasn't so controlling.
Granny Jojo: What are you talking about?
Louie: Well, honey, you must admit...
[The scene flashbacks to Louie brushing his teeth. Upon spitting, he smiles at his reflection, and a thrown pair of dentures suddenly shatters the mirror]
Granny Jojo: Oh, sorry. I thought you were smiling at someone else.
[Next, they are at a store's self-checkout machine]
Machine: Please scan your items.
Granny Jojo: [Destroys the machine in a blind rage] Who do you think you're talking to?! He's my boyfriend! Mine!
Machine: [Distorted] Please place your item in the bagging... [Shuts off]
Granny Jojo: I'll stick my foot in your bagging area!
[Lastly, at the doctor's office]
Louie: Thank you for your advice, Doc. I'll make sure to eat more fiber next time.
[Louie attempts to shake the doctor's hand, but Jojo slaps it away]
Louie: You're even jealous of the exes in my X-rays.
Granny Jojo: Then why did you want to be more than just friends with Muriel?
Louie: I meant more than just Elmore Plus friends. A friend in real life. You must admit, you don't really let me see my other friends anymore.
Granny Jojo: It's just, I love you so much, Louie. I didn't realize I was stifling you. I'm sorry. Come here. [Gives him a hug]
Gumball: Aww. So, does this mean Grandpa Louie's allowed to have friends?
Granny Jojo: Maybe just one.
[Gumball is back in his bedroom with Darwin, and is again using the computer]
Gumball: Ah, he's finally got an online friend.
Darwin: Really? Who is it?
[He clicks, and an image of Granny Jojo fills the screen]