Pi, the number, is known for many things: being infinite, being the ratio of the circumference to the diameter of all circles, and... being the homophone of a food.note
This is, basically, any pun on the words "pie" and "pi". It's a good excuse to be both nerdy and intellectual, but at the same time silly and jokey. Perhaps a scientist calculating pi is followed by someone (who could be The Ditz and/or a Big Eater) asking where the pie is, or perhaps someone is made hungry by talk of pi. If a character deliberately makes a joke about pi, they're often a quirky scientist or an Extraverted Nerd.
It might also be a visual joke, such as a pie with the pi symbol written on it, or just a good old-fashioned pun, such as someone saying that math is "easy as pi".
Subtrope of Fun with Homophones. Compare Duck!, Literal Metaphor, Literal Money Metaphor, Kitchen Sink Included, Elvish Presley, Uranus Is Showing, Literal Bookworm, and "Balls" Gag for other stock puns. Also compare LOL, 69 and 420, Blaze It for other number jokes. Also compare Gratuitous Greek, since pi was named after a Greek letter.
- 20 Pi Puns to Inspire Your Nerdiness has pi jokes, most of which, naturally, are puns with pie:
- "Come to the nerd side. We have pi."
- "Simple as 3.141592..."
- "The roundest knight at King Arthur's table was Sir Cumference. He ate too much pi."
- "The worst thing about getting hit in the face with pi is that it never ends."
- "What do you do when you take green cheese and divide its circumference by its diameter? Moon pi."
- "What was Sir Isaac Newton's favourite dessert? Apple pi."
- "What is a math teacher's favourite dessert? Pi!"
- "The mathematician says, 'Pi r squared.' The baker says, 'No, pies are round. Cakes are square.'"
- "Just saw American Pi. Gave it a rating of 3.14."
- "What do you get when you take the sun and divide its circumference by its diameter? Pi in the sky."
- "How many pastry chefs does it take to make a pie? 3.14."
- "What do you get when you cut a jack-o-lantern by its diameter? Pumpkin pi."
- "What is 1.57? Half a pie."
- "What is the ideal number of pieces to cut a pie into? 3.14."
- "How many calories are there in that slice of chocolate pie? Approximately 3.14."
- In 7 Ate 9: The Untold Story, Private I goes to a cafe to order a "slice of pi". The pie in question is shaped like the pi sign.
- In Boris Zakhoder's Russian retelling (not translation) of Alice's Adventures in Wonderland, one of the poems Alice recites is about a mathematician and a little goat dividing a pie. In Russian "pie" is pronounced as "peerog", while "pee" is the Russian pronunciation of "pi" and "rog" means "horn". Therefore, by dividing a pie the mathematician gets the pi and the goat gets the horns.
- In Going Postal, there is a bit of a confusion for some characters (and for the reader) as to how the curse of the Post Office was related to a pie. It turns out it was related to the pi (Bloody Stupid Johnson built a letter-sorting machine in which the pi equaled exactly three, and mayhem ensued).
- In other Discworld books, Unseen University is known for the appetites of its wizards, causing it to have an unofficial motto of "Eta Beta Pi"—"Eat a bit of (or 'a better') pie."
- In a Criminal Minds season twelve episode, a Stalker with a Crush discovers that Dr. Reid has a thing for math puns, she has her hostage call him and tell him the answer to his question is "as easy as Pi".
- From the Doctor Who episode "Flatline":
The Doctor: [preparing to scan] Okay, let's start with pi! Even in a flat world, they would have circles! I don't mean edible pie, I mean circular pi. Which I realise would also be an edible pie.
- Odd Squad: In the episode "Training Day", after a pienado is released, an alarm sounds, with a voice reciting the digits of pi.
- Pig with the Face of a Boy has a 2-part song called "Pi and Mash" in which the numbers of Pi are recited, and then a song is sung about mash (described as "the perfect thing to go with Pi").
- In "The Pi Song", some people ask, "Would you like some pi?". The singer, thinking they meant pie, replies in the affirmative and the other people start reciting pi to him.
- "The Extended Pi Song" is a sequel to "The Pi Song", in which the singers, after reciting pi, ask, "Would you like some more?", and he says no, but they keep reciting anyway, even when he's literally saying, "Make it stop".
- In Cyberpunk 2020 and Netrunner, one of the ways of disabling hostile artificial intelligences is called "pi in the face", which causes the AI to go for a loop calculating digits of pi.
- Transformers: BotBots has the character "Chief Cherry 3.14", a robot that transforms into a slice of cherry pie.
- In Animal Crossing: New Horizons, starting from the version 1.8.0 update, players can order "π pies" from the Seasonal section of the Nook Shopping service from March 1st to 14th in honour of "Pi Day"note . To underscore the point, each pie is decorated with a "π" baked into the crust.◊ How much does it cost to order? 314 bells.
- The Outer Worlds: You can give Felix a job interview before recruiting him as a companion. With high enough Intelligence, you can ask him what the value of Pi is. His answer? "It's delicious!"
- Xenoblade Chronicles 2 has the artificial blade Poppi. As she's essentially an android, she gets upgraded across the course of the story to two additional forms, each making her appear older and designated by a punny acronym. Her final upgrade, when she resembles a beautiful young woman, is called Poppi QTπ.
- TheOdd1sOut: In "Why Pi is Awesome", James says that the main reason pi is awesome is its name— it's a number that allows people to make silly puns due to sounding like "pie".
- The Petri Dish: One strip has Thaddeus craving pie after doing many calculations involving pi.
- On This Very Wiki, the trope for someone who can calculate pi to a great many places is called Mouthful of Pi.
- This web video makes a case for why we should replace Pi with Tau in mathematics. The narration is accompanied by footage of the creator baking two pies.
- Neopets: In one April Fool's joke, the staff had Fun with Autocensors to prevent users from talking about the prank and spoiling the surprise. Since the prank involved pies in the face, it censored "pie" into "danger", "pi" into "air", and "3.14" into "numbers".
- Pusheen the Cat: The pun is given a shout-out in the strip How to Calculate Pi.
- Sporcle has the "I Like Pi" badge, earned for completing one quiz about pie and one quiz about pi on Pi Day.
- The Amazing World of Gumball: During the Joyful Burger ad at the end of the episode "The Money", Richard says he ate Anais' homework because she said it had pie in it. Anais corrects him, saying she meant the number pi.
- Animaniacs: In one episode, the teacher Ms. Flamiel has a textbook called "Mathematics: Easy as π".
- The Grim Adventures of Billy & Mandy: In the episode "Test of Time", Billy is reading a book on theoretical physics and when he gets to a formula with pi in it, he goes to get pie from the fridge.
- The Loud House: In "No Laughing Matter", Lisa mentions pi while working in her impromptu laboratory. Luan then comes in, says, "Did you say pie?!", and gives her a Pie in the Face.
- Phineas and Ferb: In "Backyard Hodge Podge," Linda hallucinates from the exhaustion of baking pies all night, and sees her pies come to life and sing a short song about pi.
- Pinky and the Brain: In one scene, Pinky wonders what pie is, meaning the food. The Brain explains what pi the number is.
- There's an example from The Simpsons that goes:
Apu: I can recite pi to 40,000 decimal places. The last digit is "1".
Homer: Mmm, pie.
- Dexter's Laboratory: Dee Dee sends Dexter on a treasure hunt to find his missing nuclear core. The first clue directs Dexter to the pies his mom has baked via it mentioning the flavors and noting pi is R squared.
- A common way to celebrate the unofficial holiday Pi Day note is to eat pie or give (hopefully) willing participants a Pie in the Face. Some math teachers in the United States use this to get their students engaged in Geometry leading up to Pi Day. On the day itself note , the teachers may often reward their students by bringing in pie to eat and/or allowing a lucky student (usually the one who could recite the most digits of pi) to pie them in the face.