It's April Fool's Day, and Timmy can't pull a joke. So he goes over to the April Fool's house, and tries to ask him for advice. But when he gets there, Stiffy and Nick constantly play pranks on Timmy, preventing him from talking to the fool.
The episode begins when it is April Fool's Day (again). Timmy is still not able to pull the "Ultmate April Fool", and gets constantly pranked on by his family. Timmy goes up to his room, then gets pranked by Sparky. After this, Timmy knows that he needs to be a better joker, so he decides to talk to the granddaddy of it all: The April Fool! Timmy wishes that he was at the April Fool's house, and when he gets there, he opens the door, and a bucket full of water falls and splashes on top of him!. He then realizes what was going on, and looks inside and sees Stiffy up on a ladder (who just placed a bucket of water on top of the door) laughing very hard. Timmy then says that wasn't funny, but she still laughed.
Timmy asks her where her brother is. She then says that he is in there, and points to a door. Timmy thanks her, and walks into the door, realizing it was fake and just a painting. He then sees Nick laughing, and holding a paint can. Timmy then tells them to stop the foolishness and tell him where the Fool is. Nick then says he is in the Kitchen. Timmy goes into the kitchen, and lights were off. He turned them on, but first, a sack of flour was on the top of the ceiling fan blades (Stiffy put it there), and flour was flying everywhere. Second, Timmy was still wet, so the flour stuck to him and created a paste-like substance. He then cleaned off his eyes with his hand, and saw Stiffy in the pantry laughing.
Timmy no longer listens to Nick and Stiffy, and tries to find the fool on his own. But he runs into several pre-set traps on his way. Once he finally finds the Fool in the library, he so was covered with flour, feathers, and grape juice, from all of the traps, the April Fool thought he was a monster. After Timmy cleaned himself a little, the Fool recognized him, and asked him what he wanted. Timmy then says that he needs simple pranking advice. The Fool then says that he came to the right place, and reveals that the library was all made up of joke books, different kinds, lengths, and years. The Fool brings Timmy all around the library, and shows him joke books dated 1700 (which was his weakness), and Timmy gets bored and walks out. He then forgets about Stiffy and nick, and walks right into a rope trap.
While captured, Timmy sees them laughing and saying "April fools!". Timmy gets mad and says that maybe they should try to play a prank on the April Fool. Stiffy denies it, and says that she knows her brother well, and he is just too good. Timmy then says that he knows the Fool's weakness (he accidentally blurted it out while showing the books), and that they should give it a shot. The three begin planning and setting the trap up. When the trap is ready, Nick goes upstairs in the library and tells the Fool that there is a 1700 joke book in mint condition on vbay for only $100. The Fool then gets excited, and marches over to the computer. When he pulls out the keyboard drawer, he sees a cockroach on the keyboard. The Fool then gets terrified, and ends up falling back on the chair. The falling chair falls on a see-saw, catapulting a bag of molasses up in the air. The bag falls right on him, and he gets covered with molasses. Then Timmy, Stiffy, and Nick show up and start laughing. The Fool says "Well, you got me", then they all laugh.
Back at home, Timmy gets called down for dinner. At the table, Timmy wishes for a cockroach to appear on his dad's plate. it then terrifies him the same way it did to the fool, and he falls back on the chair, and a bag went flying in the air. Sparky asks if it is molasses. Timmy says "Even better." Then Mr. turner stands up being pinched by a bunch of lobsters. Then everyone pauses of a second. Then Timmy says "April fools!". Then they all laugh, and then it's the end.