The episode starts with Gumball unlocking his locker while talking to Darwin about cheese and cake. When Gumball opens his locker, something wrapped in toilet paper falls out. A crowd gathers, commenting on the gross smell and look of it. As Tobias pokes it with a stick, Miss Simian appears, angrily asking what the fuss is all about. She, too, is grossed out by the object. After ripping off part of the toilet paper wrapping, it is revealed that Principal Brown was the one wrapped up, and that he was also shaved and painted green. Miss Simian cradles the principal, then demands to know who caused this to happen. No one owns up, so she orders all of them to get into her classroom, including Rocky, who was cleaning. Miss Simian threatens to put everyone in detention if no one admits to doing it by the time she gets back.
After she leaves, Gumball asks everyone for their opinion on the subject. Sussie saw Principal Brown after school, which means that whatever happened to him occurred after school. There were only four people who stayed after school - Gumball, who had detention, Penny, who was doing cheerleader stuff, Rocky, who was cleaning, and Darwin who was unable to remember. Banana Joe convinces everyone that it was Gumball, because the Principal was found in his locker, which causes everyone to glare at Gumball. He denies doing it, but promises to find out who did. He first tries to find the culprit by telling whoever did it to raise their hand. Obviously, no one raises their hand. He then tries to get everyone who didn't do it to raise their hand. Everyone raises their hand except for Alan, which causes everyone to look at him. Gumball accuses him, but Alan, annoyed, bumps Gumball and says that he doesn't have any hands. Penny tells Gumball that he should look for clues.
The first clue Gumball finds is, coincidentally, the green paint splats on Penny's pom-poms. He invents a humorous story to describe why Penny would do this to Principal Brown, but Penny reminds him that he saw her after school, which means she couldn't have done it.
The next clue was a patch of missing hair on Rocky Robinson's hand. He again invents a humorous motive behind the assault on Principal Brown, but this story is also proven false.
The third clue was a sheet of toilet paper stuck to Darwin's shoe. Gumball has trouble calling out his best friend, but he painfully brings himself to do it. Darwin immediately admits to it, calling himself a monster. As Gumball closes the case, Carmen reminds Darwin that he couldn't have done it, because she saw him on the bus after school. The toilet paper was stuck to his shoe all day.
Gumball was the only other person who stayed after school, which caused him to accuse himself, causing his classmates to turn on him. Miss Simian arrives just as he does this, which is enough proof for her to give him detention, but Gumball was able to buy himself some time by saying he was going to get a crucial piece of evidence. After a while, we hear Gumball running away and Miss Simian realizing he wasn't coming back. She offers a reward of no homework for whoever catches him, which leads to a big chase through the school.
Gumball escapes and bumps into Bobert, who was deactivated. Gumball turns him back on, and he says he knows who caused Principal Brown's injuries, which is when Gumball gets surrounded by his classmates, all eager to claim the no homework reward. Gumball begs Bobert to tell everyone who did it, and Bobert shows everyone a video, revealing exactly what happened. Principal Brown was walking down the hallway when suddenly, his office door flew open, leaving him dizzy. He then fell down the stairs, wrapping himself with a toilet paper trail that Darwin left behind, and slammed into Penny's wet painting, which covered him in green paint. Next, he fell face first into a puddle of hair-loss chemicals that Rocky spilled, which caused him to jump up in pain and fall down more stairs, right into Gumball's locker. Gumball just shrugged and walked away.
Everyone agreed that whoever opened the office door was the one responsible, so Gumball replayed Bobert's memory, zooming in on the person who opened the door. It is revealed to be Miss Simian. She erases Bobert's memory to stay innocent, obstructing justice and causing Gumball and the rest to turn on her. As she walks away and taunts the children, Principal Brown opens his office door and pops out. The door hits Miss Simian, sending her flying out the window. The kids peek out the window to see Miss Simian getting run over by the ambulance that was called for Principal Brown. The episode ends with the kids flinching at the latter event.
[Gumball and Darwin are at school. Gumball is opening his locker]
Gumball: I think cheese is better than cake, because you can have cheesecake, but you can't have cake-cheese!
[Gumball opens his locker. Suddenly, a large, wrapped object falls out onto the ground. Gumball gasps. Students all start to gather around the object]
Banana Joe: Urgh, what is it?
Tobias: I don't know!
Leslie: Ah, it smells like manure!
Alan: It looks like a rancid burrito!
Gumball: I think it just moved!
Penny: Somebody do something!
[Tobias pokes the wrapped up object with his stick]
Miss Simian: What is going on here? What are you poking...? Euugghh! It looks like a wet diaper!
[Miss Simian unravels the object, revealing Principal Brown, shaved and covered in paint]
Miss Simian: Nigel!
Students: IT'S PRINCIPAL BROWN!
[Miss Simian cradles Principal Brown]
Miss Simian: Oh, my sweet Nigel. Who would shave you, paint you, wrap you in toilet paper and shut you in Watterson's locker? Who did this?
[Alan, Molly, Leslie, Tobias, Banana Joe, Darwin, Gumball, Penny and Tina Rex look at Miss Simian]
Miss Simian: WHO DID THIS!? I want everyone in class... NOW!
[The students run to Miss Simian's classroom, revealing Rocky, who is cleaning the floor]
Miss Simian: I SAID EVERYONE!
[Rocky runs to Miss Simian]
Rocky: Eww, what's that? It looks like...
Miss Simian: We know what it looks like!
[Scene back to Miss Simian's classroom]
Miss Simian: I'm taking Principal Brown to the nurse's office!
Principal Brown: Nurse...
Miss Simian: Calm down Nigel... [Walks away and back]
Miss Simian: And if the culprit isn't found by the time I get back you're all in detention!
[Miss Simian closes the door of the classroom, Bobert is seen standing still at stairs]
Gumball: So, what do you guys think happened to Principal Brown?
Sussie: Well, I saw him at the end of school, so it must have happened after that. [Smiles]
Tobias: So, who stayed after school yesterday?
Penny: I was doing cheerleader stuff!
Rocky: I was cleaning late.
Gumball: I had detention.
Darwin: I can't remember. [Makes a silly face]
Carmen: So you are all suspects.
Banana Joe: Oh, c'mon, it was obviously Gumball!
Tobias: Yeah! Brown was found in his locker.
[Everyone looks angrily at Gumball]
Gumball: Guys, I didn't do it. But I'm gonna find out who did. And I think I know just how. Whoever did it raise your hand! [No one raises their hand] OK, whoever didn't do it raise your hand!
[Everyone raises their hand, except Alan. They all look at him]
Gumball: Aha! So you did it!
Alan: [Bumps him on the head] Dude! I don't have any hands!!
Gumball: Darn, you're good.
Penny: Aren't you supposed to... like... look for clues or something?
Gumball: Hmmm, clues... [Wanders through the classroom] Like those paint splatters all over your pompoms!!
[A big spotlight shines at Penny and everyone looks at Penny and gasps, surprised]
Penny: No, wait! I can explain!
Gumball: There's only one explanation, it was a crime of passion.
Penny: What do you mean?
Gumball: You knew Principal Brown put me in detention last night, and overwhelmed by your feelings for me, you confronted him in his office.
Penny: Please, let him go. I love him, Principal Brown!
Principal Brown: He's nothing but a rouge!
Penny: But he's noble and strong and brave and handsome! So handsome... He might the best looking guy on the whole school!
[Leslie interrupts him]
Leslie: Gumball, have you seen your yearbook photo?
[He has a derpy pose and face on the photo]
Gumball: No interruptions, please.
[Back to recreation]
Principal Brown: We all know how handsome Gumball is, but he's still in detention!
Penny: Then you leave me no choice!
Gumball: It was then that you pompom'd him unconscious-
[Penny hits Principal Brown with her pompom]
Gumball: Shaved off his hair to punish him, covered him in paint to humiliate him, wrapped him in toilet paper to keep him quiet, and stuffed him in my locker as proof of your deranged obsession for me.
[end of recreation]
Gumball: It was you!
Gumball: But I forgive you because I am madly in love with you too.
Penny: Yeah, well, that's not quite what happened. I had finally finished my painting at the cheerleaders, and I went to hang it in the stairwell. I guess it was still wet, and I must have got paint on my pompoms.
Gumball: And did anyone see you supposedly hang this alleged painting in this "so-called" stairwell?
Penny: Yeah. You did.
[Flashback to yesterday at the school stairwell, Penny hangs her finished painting]
Gumball: Hey, Penny! I love you!...Your painting! Your painting. I love your painting.
[Gumball facepalms, end of flashback]
Gumball: Haha. Oh, yeah.
[The spotlight switches off]
Alan: So if Penny didn't do it, who did?
Gumball: Hmmm. It must have been...you!
[Gumball points to Rocky but spotlight doesn't switch on]
Gumball: I said it was him!
[The spotlight shines at Gumball but slowly moves to Rocky. Rocky and the student gasps when the spotlight shines on Rocky]
Rocky: Why me?
[Another recreation begins]
Gumball: Yesterday, you were wandering around when suddenly, at the age of 27, you've realized your youth was behind you.
Gumball: Then all your hair fell out.
Gumball: When you saw Principal Brown's lustrous hairy coat, you were overcome with jealousy. And acting on impulse, you attacked him. You frantically plucked out all of his hair, dyed it the right color, and used it to cover your balding shame. Then, planning to mislead any investigation, you painted Principal Brown, wrapped him in toilet paper, and stuffed him into my locker, the perfect crime, save for one thing!
[End of recreation]
Gumball: When you stuck the new hair on your body, there wasn't quite enough, which explains THIS BALD SPOT ON YOUR HAND!
[The students gasp]
Rocky: Dude, you've got it all wrong. I got this bald spot when I was cleaning yesterday! You see, I spilled some really strong chemicals on my hand, and it burnt off the hair. See? [Rocky spills the chemicals onto his hands] AGHHHHHHHHH!
Gumball: If that's the case, how come I can just pull your hair right off?
[Gumball pulls Rocky's hair]
Rocky: Agh! Oh! Stop! Ow! No! Agh!
Gumball: Oh, OK then, I guess it wasn't you.
[The spotlight switches off]
Darwin: Who could it be? All this suspense is making me sweaty.
Gumball: Why don't you just wipe your brow with that toilet paper suspiciously stuck to the bottom of your shoe? [Gasps] CLUE! [Gumball swells up tears] I can't believe I'm gonna have to say this, buddy, but, IT WAS YOU!
[The students and Darwin gasp and the spotlight shines on Darwin]
Darwin: Yes! Yes! I did it! I'm a monster! A monster! Just lock me up. I'm a menace to society. [Darwin starts crying] Take me away!
Gumball: I rest my case.
Carmen: But Darwin couldn't have done it!
[The spotlight switches off]
Leslie: We all saw you on the bus when we went home.
Darwin: Then how'd explain the toilet paper?
[The spotlight shines on Darwin again]
Tobias: You've had it on your feet all day, dude, didn't you notice?
[Flashback to where Darwin is walking with toilet paper on his shoe then the school bus door cuts it off]
[The spotlight switches off]
Darwin: Don't remember any toilet paper!
Gumball: So it wasn't Penny, it wasn't Rocky, and it wasn't Darwin. Which leaves us with only one suspect. The only person who knew the combination to the locker Principal Brown was founded. You!
[The students gasp as Gumball points at himself and the spotlight goes on him]
Gumball: Oh, heh heh.
[The students go "Hm!"]
Miss Simian: That's all the proof I need. You're coming with me, Watterson!
Gumball: Wait! You're forgetting one bit of crucial evidence!
Miss Simian: And what's that?
Gumball: I'll just...go and get it.
[Gumball runs away]
Miss Simian: He's not coming back, is he?
Miss Simian: No homework for the one who catches him!
[The class runs off]
[Gumball runs to the library. Molly, Leslie, Tina, Rocky, Tobias, Idaho, Carmen and Anton are blocking him, then Molly kicks Banana Joe but Gumball jumps over and Banana Joe lands in Anton's face becoming a Banana toast spread. Gumball then jumps over Molly and Leslie before jumping on a ladder]
Gumball: Ahahaha! OW!
Tobias: Quick! Give me something else to throw!
[Tobias and Anton look at Idaho]
Idaho: What? Aah!
Gumball: Stop throwing stuff at me, I'm innocent!
[Gumball, Tobias, and Anton fly to bookshelves, causing Carrie, Juke, and Teri to look up from their books then Gumball jumps from the falling bookshelves, Tina tries to bite Gumball and misses, causing the bookshelves to fall on her]
[Gumball is back in the hallway, running from Tina, Tobias, Anton, and Leslie]
Gumball: Leave me alone! I'm innocent! I would never hurt Principal Brown!
Principal Brown: I think I'm feeling a little better.
[Gumball runs into his bed causing him to roll out the window and Gumball gasps]
Principal Brown: This is extraordinarily painful. It couldn't possibly get any worse!
[A school bus reverses and runs over him]
[Gumball runs into Bobert]
Gumball: Bobert? Ah! Don't turn me in! Oh, you've been switched off.
[Gumball turns Bobert on]
Gumball: Ah! Don't turn me in!
Gumball: Principal Brown was attacked, any everyone thinks it was me!
Bobert: But it wasn't you.
Gumball: Exactly! Wait, how come you believe me?
Bobert: I saw...everything.
Miss Simian: GUMBALL! Get him!
[Everyone runs toward him]
Gumball: STOOOOOOOOOOOOOP! New evidence has come to light! Tell them what happened, dude!
Bobert: I can do better than that. I can play you my memory. First, Penny hung her hideous painting on the wall.
Bobert: Then, Gumball turned up, looking love struck as usual.
Bobert: Next, Darwin walked down the stairs, trailing toilet paper like a nincompoop.
Darwin: What's a nincompoop?
[Gumball whispers "Somebody like you" in Darwin's ear]
Bobert: Then, Rocky dropped a bottle of chemicals on the floor, looking quite bold.
Bobert: And finally came Principal Brown, who's office door suddenly flew open, leaving him disoriented and dizzy. He fell down the stairs, rolling himself in Darwin's toilet paper, smashed into Penny's artwork, covering his face in paint, then fell back into Rocky's chemicals, burning off his hair, then down more stairs, wrapping himself into even more toilet paper, and finally into Gumball's locker.
Penny: But why didn't you say something before?
Bobert: Well, it was so funny, I blew a fuse. I was like, "Ha. Ha. Ha. Ha." ::[Bobert blows a fuse]
Gumball: He's done it again.
[Gumball turns Bobert on]
Penny: So, the true culprit is the person who threw open Principal Brown's door!
Gumball: Exactly. And I know just how to find out. Whoever opened the door, put your hand up. Oh, come on!
Bobert: Why don't I just replay the tape?
Gumball: Stop there! Now forward slowly. Freeze! There. Zoom in 50%. Zoom in 100%. Zoom in another 100%. Enhance video.
[It was Miss Simian who opened the door and the students gasps]
Gumball: It was you all along! We're going to tell Principal Brown!
Miss Simian: Tell him what?
Gumball: Well, we just saw on Bobert's memory.
Miss Simian: What memory?
[Miss Simian erases Bobert's memory]
Bobert: Erase memoryyyyyyy. Who am I? [In slow motion]
Darwin: That's not fair!
Gumball: How do you sleep at night, Miss Simian?
Miss Simian: Like a baby. Ahahahaha!
[Principal Brown opens his door and Miss Simian flies out the window]
Principal Brown: Has anyone seen Miss Simian?
Darwin: Don't worry, Miss Simian! We just called an ambulance!