When the kids hear Lily apparently curse, they believe that they have been a bad influence on her, and decide to change their behavior for the future.
As the kids are enjoying themselves in the living room, Rita and Lynn Sr. are heading off to the mall, because Dr. Shuttleworth of the Daycare Academy, is coming to interview Lily, and Lynn Sr. needs a more appropriate tie. Once they head out, Lynn changes the TV channel, because Dessert Storm is on right now, and Lily suddenly exclaims "dannit". This causes her siblings to gasp in horror, because they think that Lily has just said the "D" word. The siblings fear that Lily learned the word from them, because in past experiences, the kids have gotten into some predicaments that lead them to crying out the "D" word in anger, and Lily was there to witness them saying it. Worried about being a bad influence on their youngest sister, as well as worrying that if she says that word in front of Dr. Shuttleworth, she won't get into the Daycare Academy, Lincoln comes up with a plan for him and the rest of the sisters to create some better behavior for Lily to imitate so she doesn't say the "D" word in front of Dr. Shuttleworth.
The plan is set into action. Each of the siblings are tasked on reenacting the action that led them into saying the word. Throughout all of these, their faces would turn red, and are on the verge of saying the word, but they would say something else in hopes that Lily would mimic them. After nearly an hour of doing these actions, the siblings believe that Lily has forgotten all about the word. At that moment, Rita and Lynn Sr. arrive back, and begin prepping things up for Dr. Shuttleworth's arrival. One of the things they do is set a tray of snacks on the table. Lily tries to get one, but the siblings tell her not to eat them, causing her to exclaim "dannit" again, making the siblings realize that the plan didn't work.
Dr. Shuttleworth arrives, and is ready to interview Lily. Dr. Shuttleworth gives Lily several things to play with, such as a hardware set, a guitar, and a ball, but the siblings fear that Lily would do something that could lead to her yelling out the word, prompting them to confiscate the toys. When the kids become too bothersome with their meddling behavior, the parents tell the kids to leave, but Dr. Shuttleworth tells them that they should leave too, as she just wants to be with Lily. The siblings huddle up, and says that they need a plan to get Lily out of the room. Lincoln suggests on making Lisa take Lily's place, because of the fact that she wears a wig after a nuclear experiment gone wrong, and wearing dentures. The siblings take Lily away under the guise that she spoiled her diaper, and put Lisa, disguised as Lily, in Lily's place. However, Lisa begins displaying some of her smart aleck attitude, like painting complex formulaic equations, doing an impressive xylophone solo, and able to tell Dr. Shuttleworth what type of condition her eyes are in, just by looking at her glasses. This prompts Luna to tell Lisa that she needs to act more like a 1 year old, which she does by intentionally soiling her diaper.
Later, Dr. Shuttleworth is done interviewing Lily, and concludes that due to the things Lisa did, she's allowed into the academy. Just before Dr. Shuttleworth leaves, she takes the snacks on the table with her, causing Lily to exclaim "dannit." Everybody is left horrified at this action, and the remaining siblings come to her defense by pleadingly explaining to Dr. Shuttleworth that Lily didn't mean to say that word, and say that they've been a bad influence on her. Dr. Shuttleworth, however, laughs at this, explaining to them that Lily wasn't saying the "D" word--according to Dr. Shuttleworth, Lily was apparently trying to say "donut," and with some help, Lily pronounces the word correctly after being given a donut by the doctor.
After Dr. Shuttleworth leaves, Lynn Sr. and Rita start cheering about Lily getting into the daycare academy, while the kids are glad at the fact that they apparently weren't a bad influence on their youngest sibling. However, as they cheer, Charles comes by, and snatches Lily's donut, causing Lily to cry out an actual (more offensive) curse word in fury (which is bleeped out), causing the family to look on, and gasp in sheer horror.
TNA - Leni saying "Delete" repeatedly could be a reference to Broken Matt Hardy's catch phrase.
Grawlixes - The random characters used to cover up Lily's swearing on the title card are known as grawlixes, which are "typographical symbols standing for profanities, appearing in dialogue balloons in place of actual dialogue".
Teletubbies - Lily's appearance on the title card resembles the Sun Baby from the show.
Sesame Street - When Lynn Sr. mentions a bird with a tie playing the saxophone, it is a homage to the Sesame Street character "Hoots The Owl."
Wii - The game remote Lincoln was using in his flashback of yelling out the "D" word highly resembles a Wii Remote (Wiimote), and the joke of Lincoln accidentally tossing the remote into the TV is a reference to how most people who own Wiis damage their TVs or surrounding walls due to neglecting the use of the remote's wrist strap.