It's April Fools Day, which brings out the merry prankster in Little Pete and has everyone in his vicinity fearful of his antics. Principal Schwinger (Adam West) is planning his annual assembly featuring The Up With Personal Hygiene Singers, and vows that Little Pete will not ruin his precious ear-cleaning show. When Schwinger finds out Little Pete has something in store for him and the troupe, he hires Pit Stain and his cronies to help put a stop to their common enemy. Pit Stain is able to manipulate Nona to tell him — with Schwinger listening in — on the prank in store. Schwinger apprehends Little Pete from class and detains him in his office, where Pete falls down a trap door and is trapped in the school basement.
As the assembly gets underway, Little Pete's plan begins to formulate with Nona busting him out "right on time". Monica and Wayne (the latter being the only one who doesn't know what's going on) meet up with them to put the prank into motion, unveiling three oil drums filled with Schwinger's cafeteria food of choice, creamed corn. However, the group is caught by Pit Stain, who alerts Schwinger that Little Pete is out of the way. As Schwinger gets on stage for a cotton swab/giant ear skit, it's revealed that Pit Stain is on it and helps Pete set up the oil drums and hooking them into the giant ear. As Schwinger and the singers begins to clean the ear in song, Little Pete turns on the hoses and sprays Schwinger and the troupe with creamed corn coming out of the ear to the delight of the students. Little Pete comes out with his co-conspirators and proclaims to Schwinger "April Fools!". Big Pete narrates that it went down as the "greatest prank Wellsville had ever seen."
"This is 'Last Laugh'. And these are its tropes":
- April Fools' Plot: The premise of the episode.
- Batman Gambit: Little Pete anticipates all off Schwinger's moves, including having his conversations under surveillance, in order to successfully pull off his prank. Batman himself, Adam West as Schwinger, thinks he gets one of his own when he tells Pete not to leave his office chair; when Pete does, he falls into a trap door down into the school basement. Unfortunately for Schwinger, Pete reverse-gambitted him by planning on going down the trap door.
- Blazing Inferno Hellfire Sauce: Little Pete pranks Nona by putting Krebstar Atomic Hot Sauce into his tuna surprise and having her taste it.
- The Con: The episode involves a massive prank wherein everyone, including the bullies, are in on a prank to destroy the dreaded dental hygiene skit the principal loved so much.
- Cool and Unusual Punishment: The Up With Personal Hygiene Singers are this for the student body.
- The Dreaded: Little Pete on April 1st.
- Eye Open: The episode starts with Big Pete's eye opening.
- I Lied: Little Pete had promised Nona he wouldn't prank her.Nona before the atomic hot sauce kicks in: YOU PROMISED!Pete: April Fools!
- Large Ham: Adam West as Principal Schwinger, especially during the assembly.
- Loose Lips: Wayne the Pain can't stop talking about the unspoken prank Little Pete has in store.
- Mistreatment-Induced Betrayal: Nona rats out Little Pete's prank after he pranks her. Or so Schwinger thinks.
- Noodle Incident: One of Little Pete's pranks "freeze-dried Cuba".
- Not the Fall That Kills You…: Little Pete, and later Wayne, falls straight down from Schwinger's office to the basement floor, completely uninjured.
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Paranoia Fuel: Little Pete plants seeds of this into everyone, especially Principal Schwinger. - The Prankster: Little Pete loves April Fools' Day.
- Rivals Team Up: It's revealed in the end that Little Pete and Pit Stain are in cahoots to humiliate Schwinger.
- Soundtrack Dissonance: Classical music from Pete's class is overlayed with a SWAT team infiltrating the school coming to grab him.
- Spit Take: Dad when he accidentally puts Krebjax in his coffee instead of sugar, after being foiled by Little Pete anticipating that he would think the sugar was in the Krebjax.
- To Catch Heroes, Hire Villains: Schwinger hires Pit Stain to help stop their common enemy Little Pete. Unfortunately for Schwinger, Pit Stain is in on it too.
- Trap Door: Little Pete gets caught by one in Schwinger's office, dumping him into the school basement.
- Unspoken Plan Guarantee: The entire episode after the opening intro is this; everything shown goes exactly how Little Pete needs it to go down.
- Your Approval Fills Me with Shame: Nona feels a little guilty for handing Little Pete to a gleeful Schwinger.
