Happy Pi(e) Day! Here’s the 14 Sweetest Vintage Photographs of Celebrities Indulging in Pie _ Old US Nostalgia

March 14 is Pi Day, because the date (3/14) contains the first three digits of the number pi, or π, the ratio of a circle’s circumference to its diameter.

But if we’re being honest, most people don’t get excited about Pi Day because they love geometry—they celebrate the holiday because it is a great excuse to eat pie. It’s also a great excuse to enjoy these historic photos of celebrities making, serving, or eating pie.

Founded in 1988 by physicist Larry Shaw, March 14 was selected because the numerical date (3.14) represents the first three digits of pi, and it also happens to be Albert Einstein’s birthday—the perfect pi-incidence.

The first Pi Day celebration took place at the Exploratorium (Shaw’s place of work), a San Francisco-based interactive science museum, and featured a circular parade and the eating of fruit pies. The festivities have gotten larger each year, and now include webcasts and a virtual party in Second Life (an online virtual world). It wasn’t until 2009, however, that it became an official national holiday when the U.S. House of Representatives passed legislation.

Why all the fuss about pi? The Ancient Greek mathematician Archimedes is most commonly credited with being the first to accurately calculate the estimated value of pi. Since it is an irrational, transcendental number, it continues on to infinity—the pi-ssibilities are endless! The seemingly never-ending number needs to be abbreviated for problem solving, and the first three digits (3.14) or the fraction 22/7, are commonly accepted as accurate estimations.

In mathematics, this infinite number is crucial because of what it represents in relation to a circle—it’s the constant ratio of a circle’s circumference to its diameter. Pi is also essential to engineering, making modern construction possible.

Since the mid-18th century pi has also been represented by the Greek letter π. In fact, the word “pi” itself was actually derived from the first letter of the Greek word perimetros, which means circumference.

Stan Laurel, wearing a dress, looks at Oliver Hardy and another actor covered with pie in a movie still.

Frances Gifford feeds a forkful of pie a la mode to Pat O’Brien while on tour with the Hollywood Victory Caravan, 1942. The Caravan was a tour of Hollywood stars to support the American war effort.

Hank Mann, Chester Conklin and James Finlayson dress as chefs and prepare to throw pies in a still from The Perils of Pauline directed by George Marshall, 1947.

Margaret Lockwood laughs after receiving a pie to the face from Joan Young in a scene from the 1948 slapstick comedy The Cardboard Cavalier.

Restauranteur Howard Johnson sits among over a dozen cherry pies, sampling them to find the perfect recipe.

Milton Berle gets a celebratory pie in the face with the help Lanny Ross on an episode of The Swift Show, circa 1948.

In an episode of I Love Lucy, Lucille Ball enters a baking contest, but as the competition escalates, a pie fight ensues.

In another episode of I Love Lucy, Lucille Ball’s character does a sketch that requires a seltzer bottle and a banana cream pie.

Young television stars Glenn (left) and Ronnie Walken, later film star Christopher Walken, roll out dough for pie crusts at their father's bakery, circa 1955.

Hugh O'Brian and Natalie Wood enter a pie eating competition during the Thalians Beach Ball in Malibu, California. July 15,1956. (Photo by Earl Leaf/Michael Ochs Archives/Getty Images)

Sandra Dee prepares a massive cream pie in the 1962 film If a Man Answers.

This promotional image for the 1965 film The Great Race is a still from the pie fight scene in which approximately 2,500 fruit and custard pies were thrown.

Peggy Lee and Dean Martin perform a duet of the song “You Was” which features a lyric about sweet potato pie. For the video, Martin’s head was actually protruding from a 22-inch sweet potato pie.

Mick Jagger looks on as someone approaches Brian Jones from behind, ready to throw a pie at him during a medieval inspired feast to promote their album Beggars Banquet in 1968.