Any time George and Harold rearrange the letters of a sign so that it says something ridiculous.
A florist's shop that says "Pick Your Own Roses" becomes "Pick Our Noses".
The school sign saying "See Our Big Football Game Today" becomes "Boy Our Feet Smell Bad".
Book 2: A furniture store sign that says "Come In And See Our Pretty Armchairs" becomes "Come and See Our Hairy Armpits".
Book 3: The school menu advertising "New Tasty Cheese And Lentil Pot-Pies" becomes "Nasty Toilet Pee Pee Sandwiches".
The school sign that says "Don't Underestimate Our Good Teachers" becomes "Our Teachers Don't Use Deodorant".
Another one has the same board saying "Pizza Palace Field Trips are Today" which becomes "Please Don't Fart in a Diaper".
A school bulletin board that says "People—Please Wear Your Socks On The Gym Floor" becomes "Please Go Pee-Pee On Your Socks For Warmth". The letters they didn't use even spell out "Y LOL" (Why LOL)!
Another board that says "Have A Blissfully Grand Retirement, Ms. Ribble" becomes "Ms. Ribble Really Needs A Breath Mint".
Book 6: A bulletin board saying "Please Wash Your Hands After Using The Toilet" becomes "Please Wash Your Hands In The Toilet". And Melvin falls for it!
A sign at a school entrance saying "National Fine Arts Academy" becomes "National Fart Academy".
Another sign saying "Check out our school's big internet website at www.jhes.com" becomes "We shake our big butts when we swim in the toilet".
Book 8: A sign saying "Push Button to Open Door" becomes "Push on Butt to Open Door", and a group of teachers fell for it straight.
Book 11: A sign at the hallway saying "Candy Bar Fund Raiser" becomes "Canned Barf Day".
Book 12: A sign saying "Student and Teacher Art Fair Starts Wed." becomes "Teacher Farts Stain Underwear".
George and Harold's comics take a different approach to the aforementioned joke: many of them feature a Running Gag where a sign says one thing, but then it gets sliced, burned or smashed in half and says something else. Some examples:
"At Bob's Diner, you'll find that we pick the best ingredients. Your nose knows the difference!" becomes "At Bob's Diner, we pick your nose."
"Heyman's Gifts: Who makes the best gifts and cuts the most delicious cheese? We do!" becomes "Hey, who cut the cheese?"
"My homemade buttermilk bread smells delicious! It's awfully good" becomes "My butt smells awful."
"It's fun to shop, eat, and drink out of the mall. All of the stores have clean toilets and big sales!" gets turned into "It's fun to drink out of the toilet."
"I drink delicious warm apple cider from Pittsburgh's Fruit Juice Company!" becomes "I drink armpit juice."
"I went to Bob's Pools to buy my pool! Now I dive in my pool, swim under the waves and wear a big smile!" becomes "I went poo-poo in my underwear."
Book 1: The Adventures of Captain Underpants
The copyright page for the first book◊ has a hidden gem: a small box that says "Sturgeon General's Warning: Some material in this book might be considered offensive by people who don't wear underwear." Capped off by a drawing of a fish with a cap and medal next to it!
Mr. Krupp recalling the pranks George and Harold have pulled throughout the years, one of them being the time they rigged the PA system to play "Weird Al" Yankovic songs for an entire school day.
Captain Underpants uses a pair of underwear to incapacitate Dr. Diaper, and we get this exchange:
George: Whered you get the extra pair of underwear?
Captain Underpants: (wearing a barrel) What extra pair?
When the boys first hypnotize Mr. Krupp, they take the incriminating videotape (of them pranking the school football game) that Krupp was using to blackmail them. Thats when Harold takes the opportunity to replace it with one of his little sisters old Boomer the Purple Dragon Sing-A-Long tapes. Then later, when Mr. Krupp is turned back to normal, he takes what he thinks is the security camera tape to the schools football team, the Knuckleheads. They wind up enjoying the video so much, they change their name to the Purple Dragon Sing-A-Long Friends!
The name change didnt go over too well with the fans, but hey, whos going to argue with a bunch of linebackers?
Book 2: Attack of the Talking Toilets
P.E.T.T: People for the Ethnical Treatment of Toilets. In fact, all of the disclaimers before the Flip-O-Rama in each book.
George and Harold propose making a robot urinal called the Urinator to fight the Turbo Toilet 2000, only to decide that "they would never be able to get away with that in a children's book". Made even funnier by the fact that this conversation was taken verbatim from one between Dav and his girlfriend over his original idea for the book.
Book 3: Invasion of the Incredibly Naughty Cafeteria Ladies from Outer Space (and the Subsequent Assault of the Equally Evil Lunchroom Zombie Nerds)
Mr. Krupp hiring new lunch ladies is probably a lot funnier for grown-ups.
Mr. Krupp: Do you have any experience? Alien: No. Mr. Krupp: Do you have any credentials? Alien: No. Mr. Krupp: Do you have any references? Alien: No. Mr. Krupp: You're hired!
Another moment from the fifth book is how George and Harold defeat Wedgie Woman. By disguising several cans of hair remover as spray starch. The funniest part is that not only does Wedgie Woman lose her hair, but so does everyone else! Well, except for Captain Underpants, who was already bald to begin with.
Harold: Aaugh! My mom's gonna lay hard-boiled eggs when she sees me! George: Relax. Our hair will grow back! Harold: That's easy for you to say. Your hair was only half an inch long!
Book 6: Big, Bad Battle of the Bionic Booger Boy, Part 1: The Night of the Nasty Nostril Nuggets
When Melvin (as the Bionic Booger Boy) sneezes, he ends up splattering the chalkboard with mucus. Ms. Ribble advises him to cover his mouth... which ends up making things ten times worse as it turns him into a snot-based Action Bomb.
At one point Mr. Krupp shows up in Ms. Ribble's class and demands to know why everyone is wearing raincoats and umbrellas. Then Melvin sneezes, and the next page has Krupp returning to the classroom with a raincoat, an umbrella, and a fresh set of clothes.
Book 7: Big, Bad Battle of the Bionic Booger Boy, Part 2: The Revenge of the Ridiculous Robo-Boogers
After Melvin and Mr. Krupp suffer a "Freaky Friday" Flip, George and Harold pull up a mirror to prove it to them. This exchange occurs:
Earlier, when Deputy Dangerous finds out he's turned into poop, he looks in the mirror. He yells, "What the...I'm a piece of poo!" but his reflection yells, "What the...he's a piece of poo!"
Some of the Fun Facts at the end of the Full Color versions of the books are hilarious. For example:
You might notice a theme in George and Harolds comic books: The gym teacher always gets attacked by the villains, but nobody seems to care. This theme occurs again and again because many* of Dav Pilkeys former gym teachers were REALLY, REALLY MEAN to him. So let this be a lesson to gym teachers all over the world: Be nice to your students, or some day they might grow up and get revenge by making fun of you in their epic novels! (*Note: Davs lawyer told him to use the word many.)