Squidward is in the bathtub, listening to the radio, but is disturbed by SpongeBob and Partick who are playing with SpongeBob's old baby toys that he found in his attic. SpongeBob and Patrick act like infants, then Squidward comes out and yells to them to stop making noise and act mature, however SpongeBob and Patrick don't listen to what he said. But he slips on a toy boatmobile, where his head lands on the scooter, which speeds into Squidward's mailbox, causing him to hit his head there, causing him to act like an infant himself.
A claim by doctor from clinic that Squidward that he developed a mental disorder called "head-go-boom-boom-itis" that means he is mentally and socially an infant but still aging as an adult. And is temporarily by doctor so his head safe from any blows to the same body part. However, later at SpongeBob's pineapple, when SpongeBob tells Squidward it's time for food, Patrick hurts his head by lifting him up all the way to the ceiling. SpongeBob reminds him that they are supposed to protect Squidward's head, not mess it up. When SpongeBob tries to feed Squidward, he does not like his food and spits it all over SpongeBob. Patrick licks the food off SpongeBob's face and thanks Squidward for sharing. Then, they try to entertain Squidward with games. They start off with "Kelpy Cake" (parody of Patty Cake), but when Squidward does it, he ends up slapping SpongeBob and Patrick, sending them flying into the air, and going out of the house into the street. SpongeBob and Patrick follow him, where a truck is about to hit Squidward. The truck driver falls asleep, but Patrick is able to protect Squidward and lift up the road to send the truck flying. However, when Patrick puts the road back to place, he ends up hitting Squidward's head. Then, SpongeBob and Patrick go back inside and put Squidward in a cage. He ends up crying for several more days. Then, a few days later, SpongeBob goes to work with Patrick and asks him if he can watch Squidward while he works, but Patrick, tired from taking care of Squidward, falls asleep on a table. SpongeBob informs an angry Mr. Krabs that Squidward has the mind of an infant and can't work. Mr. Krabs doesn't care because he has many customers begging to give him their money outside the door(literally). SpongeBob gets an idea. He brings Squidward to the cash register and puts him in a high chair. When Squidward blows his head on the cash register, SpongeBob duct-tapes him to the seat so he won't bang his head. When Mr. Krabs lets the customers in, Squidward sucks on a customer's hand and head and SpongeBob stops him. SpongeBob gives Squidward the order papers to write orders on, but Squidward instead doodles on them and throws them into the kitchen. SpongeBob asks him if it will be for there or to "goo". SpongeBob peeks out the order window and sees Squidward doodling on Nat Peterson's face. Nat screams and ends up running out of the restaurant. Pilar scolds Squidward for not taking an order. Squidward types in something then he bangs his jaw on the cash register again and wails violently. SpongeBob thinks Squidward is crying because Pilar yelled at him and SpongeBob tells Pilar he aughtta be ashamed. The customers notice the horrible stench of Squidward's dirty diaper and Mr. Krabs tells SpongeBob to change it. Everywhere he goes to change Squidward's diaper, people are sitting or getting condiments from or walking on. Mr. Krabs tells him to go out back, where the food is prepared, and change it. The customers are disgusted and leave. Mr. Krabs tells SpongeBob to get Squidward out of his restaurant. SpongeBob cries and tells Mr. Krabs if Squidward isn't welcome there, he's not staying either. He ends up slipping on Squidward's baby rattle and winds up in the kitchen, where he bangs Squidward's head on the frying pans and the fire machine. Squidward falls and ice comes out of the machine and lands on Squidward's head, turning him back to normal. SpongeBob is relieved that Squidward is "grown up again" and a confused Squidward asks why he wouldn't be grown up. He notices that he's wearing a diaper and that it's full. When SpongeBob is about to tell Squidward that he was going to change him, Squidward tells SpongeBob to not say another word about that experience, ever. SpongeBob then replies, "Kids, they grow up so fast."
- When baby Squidward draws on Nat Peterson's face, Nat says, "MY FACE!!!, MY FACE!!! Also my leg, but MOSTLY MY FACE!!!", being the first time after "Shuffleboarding," where the "My leg!" gag hasn't been heard, but referenced.
- Running Gag: Someone getting hit on the head (including Squidward's house).
- This is the second time in this episode Squidward had a change in appearance due to his injury. The first episode where he changed appearance was "The Two Faces of Squidward."
- When Squidward hit his head, it expanded; but it is unknown why his nose shrunk.
- SpongeBob was comforting Squidward, while Patrick watched TV. This is the same as in "Rock-a-Bye Bivalve," where SpongeBob comforted Junior.
- The doctor said that if Squidward received too many blows to his head, the condition may be permanent. However, at the end of the episode, blows to the head returned Squidward to normal.
- It is possible the doctor that told SpongeBob this might not have known what he was talking about, or didn't know, and made the whole thing up
- Some of the toys in the baby toy box resemble the one from the Crane from "Skill Crane" including an octopus and a teddy bear.
- This and "Gary in Love" both end with SpongeBob saying "They grow up so fast."
Home video releases
- SpongeBob SquarePants: The Complete 9th Season