Stu gets Tommy and the gang a new present, The Kiddie Karnival, and spends almost the entire episode trying to build it. Meanwhile, the Rugrats use the box that the toy came in for some exciting imaginary adventures of their own. - Description from Klasky Csupo
Stu has ordered the Kiddie Carnival, an elaborate theme park play set, for Tommy. Unfortunately, it has to be assembled, though Stu feels that he can mange it, as he's a professional toymaker. However, once Stu looks at the complex instructions and the many parts to assemble he begins to feel discouraged before he even starts.
Tommy, bored from waiting for Stu to finish, climbs into the box all the parts came out of. Tommy imagines the box as a race car, and zooms around the track, until Didi finds Tommy in the box. Didi plucks him out, and Stu takes the box down to the trashcans at the curb. Tommy is sobbing and now cries with his La Sabre sound. Chas happens to walk along as Stu is throwing out the box and comments that he knows someone else who bought a Kiddie Carnival for their kid(s) a few months ago. When Stu asks how he managed it, Chas says it was still uncompleted last he heard, which further discourages Stu.
When Stu heads back inside, Chas looks closely at the discarded box and decides he can use it, so he takes it home and sets it in the living room. Chuckie discovers the box and crawls inside, which he imagines it as a spaceship, where he travels the galaxy, meets familiar aliens, and is almost eaten by a bad alien. At that moment the box is pulled away from Chuckie. Chas apologizes and explains he needs the box, then loads it up with used exercise equipment that he takes to the DeVille's house.
Betty dumps out the equipment and leaves the box in the living room with the twins. Phil declares the box to be a house, while Lil says it's a dark, scary cave. The two argue before they decide it's a house and a cave. Phil lounges next to a bear, but when Lil tells him to get away from the bear, he claims it's a couch and the two fight.
Betty separates the fighting twins, and invites Chas to go with her and Howard while they donate the exercise equipment, but Chas declines and explains Chuckie's babysitter has to go home at five. Betty insists, and tells Chas that he can drop off Chuckie at the Pickle's house with Phil and Lil. Chas doesn't think it's a good idea, saying they rely on Didi and Stu too much. Betty insists it's fine, and after the box is deposited by the curb again, Chuckie and the twins are taken to the Pickle's house.
It's revealed that Stu is having a very difficult time assembling the Kiddie Carnival, and accidentally breaks a part when the doorbell rings. Didi welcomes the babies, but Stu is disgruntled with watching them due to his difficulties assembling the Kiddie Carnival. Didi takes them outside, where Lou is "watching" Tommy and Angelica. Angelica has almost convinced Tommy to smash his grandpa's foot with a hammer, but the arrival of his friends distracts them. Tommy tells them about his race car that his mom took away, prompting Chuckie to talk about the spaceship Chas took away, and the twins mention their house/cave as well. Angelica isn't interested and demands proof for these things, which they don't have.
Stu, meanwhile, has fetched the box to check for a spare part (even though Didi insisted it was empty when she gave it to him to throw out), and complains about how he found it in front of the DeVille's house. Stu is angry that they "stole" his box, but Didi reminds him he threw it out, and that it was, indeed, empty. Didi deposits the box in the backyard, where Tommy is happy to see his race car, Chuckie his spaceship, and the twins their house/cave. Angelica says it's just a box and tries to take it away from the babies. Didi witnesses this from the house, and brings a highly discouraged Stu over to watch them, too. Stu recalls a shoebox he turned into a submarine (until Drew stepped on it) when he was young, and comes up with an idea.
In the backyard, Tommy, Chuckie, Phil, and Lil all tug on the box at once to take it away from Angelica, but the box rips. Angelica feels satisfied and waits for them to be upset, but Chuckie picks up a piece of ripped box and imagines he has wings, and soars through the sky. Tommy resumed cry with Crown Victoria sound and Phil and Lil cries with Asylum and Lumina sound. Tommy picks up a second piece and imagines it to be an exotic mask and dances by a jungle campfire. Then the twins pick up their own pieces and now have swords to use in a sword fight with each other.
Angelica takes away all their box pieces and shrieks "You dumb babies! It's just a stupid BOX!" Didi catches her doing this, and Angelica lies, saying the babies made her do it. Stu, however, ignores her and invites them all inside, because he has a big surprise for them. Angelica exclaims he finished the Kiddie Carnival and runs inside shouting "Me first! Me first!", but is shocked when she enters the house while the babies are delighted.
Later, Chas, Betty, and Howard return to Didi and Stu's, and find the unassembled Kiddie Carnival in the trash. Howard notes that the babies seems to be taking the news well, judging by the laughter and excitement from inside. When Stu answers the door, he cheerfully greets them and invites them to grab a box. His surprise, it turns out, is many empty boxes that Stu normally ships the toys he invents in. The babies are having a wonderful time with all the boxes, but Angelica sits alone, saying she just doesn't get it. A box is tossed on top of her, and the episode ends.
- There is later an episode of Spongebob Squarepants which has a similar plot. In this case however, Spongebob and Patrick ordered a large TV just so they could play with the box and Squidward can't understand why.
- The "Tribal Chant" sound effect in this episode's closing credits is the same vocalization that appeared in The Walt Disney Company's 1945 Goofy short "African Diary", a 1954 Walt Disney Cartoon Short “Social Lion, and a 1956 television special “On Vacation with Mickey Mouse and Friends".