Luan pranks the entire household every year on April Fools' Day, but this year Lincoln has a plan to avoid her pranks.
Lincoln is explaining to the viewers that tomorrow is April 1st, which is April Fools' Day. Luan becomes a sadistic pranking monster on this day every year, so Lincoln, the rest of his sisters, and their parents are all scared of this day. He shows some footage of the past April Fools Days, showing that Luan is unstoppable (like nailing the living room furniture upside down, placing chickens in the living room, covering the entire house with present wrapping paper, trapping all of her siblings in a giant block of gelatin, and shaving all of the Loud pets' fur and feathers off). Lincoln plans to stay in his room for the entire day, while his sisters are preparing to defend themselves. Lisa builds a bomb shelter to take cover in and the others add body protection, mostly consisting of plastic bubble wrap.
After boarding up his entire door, Lincoln calls up Clyde if he wants to come over. However, Clyde refuses to come over, knowing about Luan's pranking spree. Just then, Lincoln gets a text from Ronnie Anne telling him that she's coming over to give him a present. Lincoln is scared because he'll have to exit the confines of his room and if Ronnie Anne gets pranked, she'll severely hurt him. Clyde suggests to Lincoln that he go face-to-face with Luan and call off April Fools. He does so, but Luan refuses to back down, stating that anyone who falls victim to her pranks is fair game. When Lincoln heads back to his room, he comes up with a plan to prevent Luan from pranking all of them. He tells his sisters that if they work together, they can take Luan down. That night, in Luna and Luan's room, Luna gives a bird-like call signal to her siblings. Everybody then enters the room and tie-down Luan, trapping her in a cage and keeping her fingers together with Chinese finger traps. The siblings mock Luan's situation while she looks on in anger.
The next day, however, the siblings are shocked that Luan broke out of her cage and that she could be anywhere in the house. Almost immediately, the pranks are being set off so they all take cover. As all the siblings take shelter in Lincoln's room (except for Lisa, who takes cover in her bomb shelter), Lincoln remembers that Ronnie Anne is coming by later. Not wanting her to get pranked, Lincoln decides that the best thing to do is to set off the pranks in the house to save Ronnie Annie from them. The sisters wish Lincoln good luck, with Lucy saying she will prepare for his impending funeral.
Lincoln runs downstairs and heads to the kitchen where the entire floor is covered in grease. After taking one step, he loses his footing, gets socked in the face by a boxing glove on a spring, and gets attacked by vicious raccoons, all while Luan looks on with pride. Mr. and Mrs. Loud, who is also terrified by Luan's pranking spree, begs for Lisa to let them into her bomb shelter, which she does. As the sisters hide in Lincoln's room, Lori suggests that they ration the food supply, but Lana has eaten it all, much to everyone else's exasperation. Leni nominates herself to get more food from the kitchen, but thanks to a bunch of misleading signs placed by Luan she wanders out of the house and into who-knows-where in the city.
Lincoln then takes on the bathroom where he is covered in flour, sprayed by the sink, and attacked by another vicious raccoon. Next, he tackles the living room which results in him getting flung into the ceiling and getting stuck in flypaper. The last thing Lincoln has to do is set off all the pranks in the bedrooms (with Clyde taking on Lori and Leni's room). When Clyde collapses on the sidewalk, Ronnie Anne arrives and is shocked to see Lincoln in critical condition. Luan declares victory, but Lincoln claims that he did it to save Ronnie Anne from humiliation. Luan then reveals that she called Ronnie Anne to come over, thus giving a reason why Lincoln had to leave his room and that she is the final part of her plan. As Ronnie Anne pulls out a pie, Lincoln embraces for impact, but she instead pelts Luan with the pie. It turns out that Ronnie Anne appreciates Lincoln sacrificing himself to Luan's pranks for her and pelted Luan instead of him as a sign of gratitude. The two then depart so Ronnie Anne could put Lincoln's eyebrows back on while Luan looks on with pride, saying that Ronnie Anne is a keeper.
As Lisa, the parents, and the remaining sisters exit their shelters, they are relieved that they didn't get pranked. However, they realize that Leni's missing and Lisa deduces that the signs that mislead Leni earlier are the cause of this. Mr. Loud prompts everybody to get in the car, but when they start it the airbag explodes, splattering blue paint all over the interior of the car. As the family yells out Luan's name in fury, the latter is depressed that April Fools is over and that she's feeling blue now (alluding to the blue paint joke she just pulled off).
There was an extra prank that was removed from the finalized episode due to running time.
This prank involved Luan setting up cups filled with water all over Lincoln's floor. Lincoln had to drink all of them to get out of his room. But when he opened the door, he found more cups in the hallway. He had to drink those as well, and when he got to the end of the hallway to use the bathroom, the doorknob came off, much to his despair. He then collapsed, unable to go to the bathroom, with Luan taunting him.
Lincoln depranking the bedrooms were also cut along with Clyde depranking Lori and Leni's bedroom, while Lincoln depranking the kitchen, bathroom, and living room was in this episode. The aftermath of both was shown, though.
The episode's title card was originally going to be green and yellow.
Ronnie Anne is the only character in this episode who didn't suffer a bad prank or get harmed in some form.
This episode reveals that on April Fools' Day, Luan turns into a cruel, ruthless, and unforgiving lunatic.
Luan had an embarrassing video of Lincoln just like it was revealed in "Making the Case".
April 1st is shown to be on a Sunday, meaning the episode might take place in 2012 or 2018.
During production, the gelatin that Luan traps her siblings in was orange, but in the final version, it is red.
On a past April Fools' Day, Luan shaved off Lori's eyebrows. On the eve of the current April Fools' Day, Lori's talking on the phone with her boyfriend, Bobby, and tells him that they should cancel all their plans during April because Lori claims that if Luan were to shave off Lori's eyebrows again, it would take at least a month for them to grow back.
By the time of "Fool's Paradise", Lori's eyebrows are growing back in coarse, though they fall off when Luan begins her pranking spree.
Luan breaks the fourth wall at the end of the episode, when she tells the viewers she was feeling a little blue, as a result of the prank to her family in Vanzilla.
Innuendo: After Luan pops a bubble in Lola's bubble wrap, Lola remarks that she would need "a fresh pair of undies," implying that she wet herself.
Lincoln begs Luan to call off her pranks before Ronnie Anne comes over tomorrow, and she agrees. Lincoln seems to buy it, though Luan interrupts him, saying it is just "April Fools practice!"
Later, Lincoln uses this against her; when the other siblings have Luan locked in a cage and she demands to be set free, and Lincoln seems to agree. Luan is in disbelief that she is being let off the hook that easily, only to have Lincoln interrupt her with a biting "April Fools!"
In the United Kingdom, the final scene during Luan's montage of April Fools' Day pranks where she shaves the Loud pets is cut. Because of this, the flashback abruptly ends with the siblings covered in gelatin.
In Lincoln's footage of Luan's previous April Fools Day pranks, the siblings don't change in appearance at all. Also, at some point, Lisa should be an infant, and Lily shouldn't even be born yet.
However it is possible that all the pranks shown in the montage happened exactly 1 year before the events of this episode.
Lincoln's calendar only has 28 days, when it is supposed to have 30.
When Lincoln is about to show Luan's April Fools Highlight Reel, his comic books are on his bed. When Lincoln finishes the highlight reel, the text of his comic books is missing.
When the siblings are laughing at their jokes, Leni's closing eyes are down instead of up.
In the Latin American Spanish dub of the episode, when Lisa says "I have my suspicions.", she says it with Luan's voice.
When Lincoln enters his room for the first time, there is a control game between his computer and the toy robot, but before entering, there wasn't anything between those objects.
In the Brazilian Portuguese dub, when Lincoln talks to Clyde, he says "Ela vai cair nas pegadinhas da Luan e terminar comigo" (She'll get nailed by Luan's pranks and then pulverize me!). "Terminar" is commonly used as the equivalent for "Break up", implying that they're dating.
When the Loud family's pets are shown to have been shaven clean, Charles still has his black fur.
It's never explained how Luan freed herself from the cage.
What happened to Leni after being misled by the signs remains a mystery.
Possible: Part of Lincoln's eyes are not drawn when he was talking to Clyde by the walkie-talkie about his "planned funeral," though this could have been intentional to illustrate his eyebrows are now missing, since Ronnie Anne mentions drawing them on afterward.