Dawn is tired of her brothers going into her bedroom and invading her privacy. She has a door sign that says "NO BOYS ALLOWED" but the boys ignore it. Ricky even uses a marker pen to change the sign to "NOW BOYS ALLOWED." Dawn discovers that the boys have been reading her diary and gets mad at them. She hides the diary even further to keep it away from the boys.
Dawn tells Mae that she's had enough and she needs to give the boys a taste of their own medicine. So, she starts writing fake diary entries to mess with the boys. In the first entry, she writes about how she has a very bad mouth fungus that causes hair to grow on the tongue. And the only thing that gives her peace is scratching her tongue with the tip of her diary pen (which Nicky has in his mouth). The boys get paranoid and start avoiding getting into contact with Dawn's saliva in any way. In order to torture the boys even further, Dawn comes home with the best icecream that they know the boys would all want to eat. Dawn offers them the remaining ice-cream and they all run away from it.
Dawn writes another fake diary entry saying that she likes her brothers but she knows that two of them are plotting something against the other and are planning to take the thing that he prizes the most. After reading this, the boys become suspicious of each other. Nicky thinks that Ricky and Dicky are after him. And Ricky thinks Nicky and Dicky are after him. Dicky is concerned too but he doesn't seem to care very much. Each of the boys starts trying to bribe Dawn hoping that she will tell them what the other two brothers are planning. Ricky offers to do Dawn's homework because Dawn is a nice sister and she would tell him if anyone was going after what he prizes most: his perfect attendance record. Dawn plays along but refuses to tell Ricky anything. Nicky bakes Dawn's favourite muffins and he hopes Dawn will tell him who is trying to go after his valued possession: his frying pan. However, Dawn refuses to tell Nicky anything. Dicky tries to give Dawn her favourite lamp as a present because she is his favourite sister. He's worried that Nicky and Ricky are planning to mess with his hair. Dawn takes the lamp and refuses to tell Dicky anything.
Later, Dawn and Mae are laughing in Dawn's room about how Dawn has been messing with her brothers. Mae wishes her little brother was dumb enough to read her diary so she can mess up with him like that. When Dawn and Mae leave the room, it turns out the boys were hiding in the room hoping to find more details about how the other two brothers were plotting against him. But now they know the truth: Dawn was just messing with them. They've got to get her back!
Later that night, Dicky knocks on Dawn's door while she's asleep and asks if he can come inside. He tells Dawn that he knows his brothers are up to get him and he will mess with them before they can get to him. Right after Dicky leaves, Dawn calls Mae to tell her how well the prank is going. Early the following morning, Mae arrives at the Harpers' house before the boys wake up so that she can witness whatever Dicky did to Nicky and Ricky.
A few moments later Dicky comes screaming that his brothers are out for blood. Nicky and Ricky enter the room completely bald. Dawn is shocked. Dicky says he shaved their heads because they were going to do something bad to him first. And how did he find that out? Dawn's diary? And why would Dawn write such a lie? Dawn feels compelled to tell the boys the truth about the fake diary entries and apologizes for messing with them. She tells them they should respect her privacy but they manage to make her feel guilty for causing more harm. The boys run into the kitchen and start laughing about how they fooled Dawn. They reveal that they were just wearing flesh-coloured swim caps to trick her.
Dawn enters the kitchen a few minutes later with her head shaved too. She tells them that she felt bad for messing with them and so, she got her hair shaved too to show that she cared. Nicky and Ricky feel guilty and reveal that they were faking with bald caps. Dicky blames himself for causing the whole thing. So, he takes scissors, ready to cut his hair. Dawn tries to stop him but he makes a big cut anyway. Dawn then reveals that she was wearing a bald cap too. She and Mae had overheard the boys talking in the kitchen about how they messed up with her. The boys were talking loud with the kitchen window was open, while Dawn and Mae were literally sitting in the living room. They all acknowledge that they went too far but all's well that ends well, right? Except Dicky is still shaved for real.
- Lizzy Greene as Dawn Harper
- Casey Simpson as Ricky Harper
- Mace Coronel as Dicky Harper
- Aiden Gallagher as Nicky Harper
- Allison Munn as Anne Harper
- Brian Stepanek as Tommy Harper
- This episode is a parody of the book series Diary of a Wimpy Kid
- This is the third time we see Dawn's room, The other two episodes were Dawn Moves Out and Take the Money and Run.
- This is the first episode not to feature Squishy Paws.
- It is revealed that Dawn's favourite muffin flavour are chocolate chip
- Nicky makes a reference to the film The Fast and the Furious.
You may view Diary of an Angry Quad's gallery here.